All language subtitles for Android-Development-for-Beginners-Full-Course-Part-2_en

in this video we are going to create a

recyclerview to show our books inside

our own books activity but before that I

am going to create a model for my book

so in my package I can say new Java

class let's name it both for this book

item I'm going to have an ID first of

all let's say private int ID this ID is

going to be unique for every book and

later on we will identify our books by

this ID after that we need a name

private string name also we need the

author private a string author I'm also

going to define an integer for the

number of pages so let's say private in

pages a string maybe for the image URL

also I'm going to define two more fields

one is called short description and the

other one is called long description

we are going to show different versions

of this description in different places

okay let's quickly create a constructor

I'm using alt + insert let's select all

of our fields and also down below this

constructor let's quickly create getters

and setters I'm also going to create a

two string method I believe it will be

useful Alt + insert just to drink let's

select all of the fields okay this is

sometimes we named these kind of classes

as poles pojo stands for plain old Java

object in which the class has some

constructor and some getters and setters

method ok let's move on and let's

implement the recyclerview dependency

into our project so if I open the layout

file let's go to the layout folder

inside this activity all books that

examine if we switch to design view you

can see that we have this recycler view

option in here and we can drag that in

our layout let's switch to a split view

and let's change the beads on high to

match parent so inside this activity we

are only going to have a recycle of view

let's also give it an ID and let's

initialize it in our Java file let's say

let's open all boats activity dot Java

class and let's initialize our recycler

view private recycler view let's name it

brokes recycler view and down in here

inside on create method let's a box

recycler view is equal to find view by

ID r dot ID dot box recycler view after

that it's time to create the adapter for

this recyclerview let's quickly do that

so in my package i can right click let's

say new Java class I'm going to name

this class pop recycler view adapter

first of all let's create our view

holder class let's say public class view

holder I'm going to name it let's say

extent recycler view dot view holder

this class after that we need a

constructor we can do that by pressing

Alt + insert and selecting constructor

before going further we need to create a

layout file for every item in our

psychology certain our layout folder

let's say new layout resource file I'm

going to name this list item book let's

minimize this project pane and let's

switch to a split view first of all I'm

going to change this constraint layer to

a card view so this fold layout file is

going to be a card view and in here I'm

going to use the material card view I

think the style is a little bit

different also let's change the beats

and height to wrap content let's also

give an ID to discard view later on you

are going to need that let's name it

parent inside our card view first of all

I'm going to create a relative layout

let's say match parent and mesh pattern

for the vitsin height and inside this

relative layout let's have some items

for example I'm going to define an image

view for the beats I believe 130 would

be fine 130 DP also for the height I am

going to say 200 TV that seems a little

bit large let's decrease that to 150

let's be with an ID I'm going to name it

IMG book let's also have a placeholder

let's say source and let's pass our I

see launcher icon after this image view

let's quickly define a text view for the

name of our book we're going to say wrap

content and wrap content for the text

style of this text by same text style

I'm going to pass bold in here beside

that let's increase the size text size I

let's move EQ below our image view let's

say layout below our ID IMG book beside

horizontally so that's a center

horizontal true I think it's better to

that's a margin top 5 DP or 7 DP maybe

that's almost it for our layout file in

here I'm just going to add two more

first of all let's say cart corner

please mount cart corner radius

let's pass 7 DP beside that let's add a

cart elevation once again I'm going to

say 7 DP in here you can see that we are

only showing the image view and also the

book name but if you remember when we

have created our book model we had more

information we are going to show those

information in two different places in

our application first of all by clicking

on every book we are going to navigate

the user to another activity and beside

that we are going to show lesser

information when the user clicks on some

arrow button on our cart view to be

precise later on we are going to create

an expandable card view which means that

for the first time that the user sees

this activity we are going to show only

the image and the book name but if the

user wants to see some more information

he or she can click on some arrow button

in here and expand our card view later

on we will create that also I forgot to

add a margin in here let's quickly do

that let's say margin and I believe 5 DP

would be fine ok now that we have

initialize our UI elements inside this

view holder class for that in here I'm

going to say private card view for the

parent let's name it parent beside that

once again I'm going to name is IMG book

and also let's say private text view

let's say txt name I believe we did not

define an ID for this text view that's

so in here for this text view let's pass

on ID let's say txt book me okay back in

our adapter class inside the constructor

of this view holder class after the

super statement let's initialize our UI

elements we have done this before

we can say parent is equal to item view

let's pass our dot ID does parent

so after creating this inner class we

can extend the recyclerview class in

here and we can pass this view holder as

the datatype of our adapter so I can say

recycler view dot adapter and I can pass

my view holder class make sure to import

the one that comes from your package

work that may put that my library dot

block recycler view adapting you'll know

that in here right now we need three

let's press ctrl + v and let's import

our methods before doing anything inside

these methods first of all above in here

I'm going to define an array list let's

say private ArrayList of different books

let's name this array list books is

equal to new ArrayList so this array

list is going to be the list of all of

the books that we are going to show in

our activity beside these books

ArrayList I'm also going to need a

context because if you remember when we

are going to use glide in our project

client library needed the context to

show the image so let's say private

context let's name it in context after

that let's create our constructor in

here I'm going to receive only the

context for the books aerialist we are

going to create a setter method let's

create that method down in here by

pressing Alt + insert once again but

select setter and let's create a setter

method for our books are released you

know that when you set your books this

way you also need to add a method in

here and that method is notify data set

changed we are adding this method

because we are going to refresh the data

in our recycler view okay let's move on

from this part and let's start working

on this get item count method but before

that I'm going to minimize this view

holder class this get item count method

as I said before is just returning the

size of items or the size of least in

our recycler view so in here i can say

nothing special is going to happen

inside this uncreate view holder method

we need to create an instance of our

view holder and we need to return that

probably all the times the code inside

this on create view holder method is

going to be the same in all cases so you

can save the copy and paste but I'm

writing in here so I can save you

let's name it view is equal to layout

inflator if you remember let's say that

from we need to pass a context in here

and we can pass the context by using

this view group let's say parents that

get context after that we can call the

Tottenham flight method in which first

of all we need to pass our layout I can

say our that layout dot list item book

after that we need the view group itself

in order to attach our layout file this

list item block to its parent and after

that I am going to pass false in order

to avoid redundancy after creating this

view object you can create your view

holder quest let's say view holder let's

name it holder is equal to new view

holder and let's pass our view object

after that I can return my holder also

this method in here can be simplified

right now you can see that this local

variable is redundant it means that you

can directly return it instead of

creating an instance of that holder

class so in here what I can say is that

I can say return new view holder and I

can pass my view once again in most

cases this is exactly the code that you

need to put inside this one create new

holder method after that down below

inside this unbound view holder method

first of all I'm going to lock something

indicating that this method has been

called in order to add a lock a bug in

here first of all I need to add a

constant after that inside on point view

holder method I'm going to say lock D

let's just say called first of all let's

set the name for our book I'm going to

say holder dot txt name that's at

let's say books that get let's fast

position let's say that get named after

that we need to show our image in which

for that we need to collide library for

that I'm going to search the internet

for Glide dependency the first link

which is a github link is probably our

first of all let's add these two

dependencies in our project inside

grading scripts inside this built at

Gradle modular inside these dependencies

I can paste them let's also check that

if we have this maven central and Google

repositories in our built at grader

project one it seems like we need to add

the maven repositories let's copy it

from here maven central and let's paste

ok let's sync our project ok it seems

dependency successfully let's switch

back to our adapter class and inside

this unbound view holder method I'm

going to say flight dot with here we

need our context which was named in

context after that let's say as bitmap

dot load we need an image URL in here

which I'm going to say it pops that yet

let's pass our position let's say that

get image run and after that we need our

image view let's say that into our

holder dot my mg book ok this way we can

show the name and image of our book I'm

also going to set an onclicklistener for

the card view parent for the time being

by clicking on this card view we are

going toast message but later on we are

going to create a book activity and we

are going to navigate the user to that

activity so for now let's say holder dot

parent dot set on click listener let's

say in the onclick listener and let's

show our toast message let's receive the

name of our book I'm going to say oops

that get let's pass our position that

okay I believe that's all we need for

now inside this book recyclerview

adapter later on we are going to change

this a lot but for now let's initialize

it inside our all books activity and

let's set it as the adapter for this box

recyclerview I'm going to define the

adapter above in here as a member

valuable so that we can have access to

this method inside different methods I

think we are going to need that let's

say private books recyclable your

adapter let's name it adapter down in

here before initializing our recycler

view adapter I'm going to say adapter is

equal to new books recycler view adapter

and let's pass our context once again

because we are inside an activity we can

pass this after that I'm going to set

this adapter as the adapter of my

recycler view let's say books recycler

view dad set adapter let's pass our

adapter also for the layout manager I'm

going to pass a grid layout manager

let's say box recycler view that set

layout manager new grid layout manager

this one first of all we need the

context let's pass this after that we

need the number of columns which I'm

going to say to after setting the

adapter we need to set the data I mean

the books area list for the time being

for testing purposes let's just create a

dummy ArrayList and let's pass it to

this adapter let's say array list of

different books let's name it pops is

equal to new ArrayList after that let's

say books that add and let's add a book

let's say new book for the idea of this

book I'm going to save on for the name

let's say 1q84 for the author let's say

Harlequin Murakami after that let's

I believe it's 1350 pages let's quickly

copy some image URL let's search for

1q84 and I think this one is good let's

paste it in here just make sure that

your images and weights that jpg or dot

PNG let's go to the next line let's see

what else do we need we need a short

description and also a long description

for the short description I'm going to

say a work of madelung variants

I believe it's about the Time magazine

for the long description I'm just going

to pass along description because we are

not going to show that yet okay after

adding this book I'm going to say

adapter that sets books let's pass our

books ArrayList before testing the

application let's quickly add the

internet permission because we are going

to load the images from Internet we need

that permission in our manifest file

above the application tag I can say

users permission and I can pass internet

permission okay let's test our

application and let's see if we can see

this put in our activity let's click on

this see all box button as you can see

we are getting a card view for our book

but we are not seeing the image if you

remember I mentioned this problem in

previous videos the reason that we are

not seeing this image is because we have

changed our manifest file we have added

the permission and because we have

changed our manifest we need to

uninstall the application and install it

once again we will do that in a minute

but before that you can see that we have

this ugly background in here I'm going

to get rid of that and beside that I'm

going to add a padding for my recycler

view right now discard view is too close

to the edges of our screen let's quickly

fix those issues so inside our activity

first of all let's delete this

background color after that in our

recycler view item I'm going to add a

margin similarly you can add the padding

on your constraint layers I'm just going

to add the margin in my recycler view

let's pass 15 I believe that's good okay

before testing the application I'm going

to uninstall it from the device so if we

in the apps and notification we can see

this my library application let's

uninstall it and let's run our

application once again this time if we

click on this CL box button after a time

we should see our image it takes some

time to load the image but after all we

can see that let's also check the

on our card here so if we click on our

card view you can see that we are seeing

this toast message which seems to be

working fine okay I think that's enough

for this video in the next video we are

going to work on that expandable card

view that I was talking about so

basically right now we are only seeing

the name and image of this book in the

next video we are going to add a little

arrow button in here in which by

clicking on that the user can see more

details about our book just before I

finish off this video once again I'm

going to say that if for any reason you

need to check the source code I will

upload the source code at the links that

you can see on the screen at make up dot

or feel free to check that if you need

and also I would love to hear your

feedback on the code that I just write

in this video we are going to work on

expandable card view that means that we

are going to show this simple card view

plus an arrow button in here an arrow

icon in which if the user clicks on this

arrow we are going to expand our card

view and we are going to show some more

information for example in this case we

are going to show the name of the author

of this book mas we are going to show

the description the short description of

this book in this video we are going to

see how we can implement that but I need

to say that this way of implementing and

expandable card view inside our

is not going to work with our grid

layouts manager it works perfect with

linear layout manager but for grid

layout manager you need some more

information we will talk about how to

implement an expandable card view in

grid layout manager later on in the

course so because of that first of all

inside my own books activity I'm going

to change the layout manager for my

recycler view to a linear layout manager

and also I am going to increase the size

of this card view so let's switch to all

books activity this one and then in here

you can see that we are using a grid

layout manager let's quickly change that

to linear layout manager we need a

context which I'm going to pass this

let's close this file for now we will be

coming back to this file and let's

switch to a split view and let's write

expandable view for this card view so

here is what we are going to do we are

going to create another relative layout

then below this one that we already have

and we are going to change its

visibility to run later on in the code

inside the recyclerview adapter when the

user clicks on our arrow bottom we are

going to change the visibility of our

relative layout to visible plus we will

add some animation for adding another

relative layout in here I am going to

add one above in here as a single child

of this court view and I'm going to put

this relative layout that we currently

have inside that so let's say relative

layout for its bits I'm going to say 200

DP and for the height I'm going to say

wrap content also I'm going to change

imageview to 200 TP if you remember I

said that because we are no longer using

a great layout manager I'm going to

change the size of this card here so

let's say 200 DP and for the height

let's say 220 I believe is fine now we

let's finish creating our relative

layout and let's move this one to inside

the first relative layout so I'm going

to copy everything but I think it's

better to minimize this relative layout

and copy everything or cut everything to

be precise and place living here you can

see that now our chord view has this

strange shape that we can fix that so if

we open this relative layout you can see

that for the height we have said match

parent I'm going to change that to wrap

wanted as soon as I do that you can see

in the preview that the height has been

okay let's minimize this one after this

relative layout I'm going to create

another relative layout which is going

to be the expanded version of our chord

view so let's say relative layout for

the width I'm going to say match parent

for the height let's say wrap content

I'm going to move it to below the first

relative layout so let's give an ID to

our first relative layout let's name

this bond collapsed relative layout once

again let's minimize it now in here I

can say below our collapsed relative

layout inside this relative layout as I

said I'm going to define some text views

I'm going to show the name of the author

of this book plus I'm going to show the

short description so first of all let's

say text view wrap content and wrap

content for its text I'm going to say

author let's give it an ID let's just

say author text I'm not going to change

the style or anything after that let's

and define another text view for the

Viets that's a wrap content similarly

for the height wrap content for its text

I'm going to put the name I'm going to

put my name for its ID I am going to say

TX the author this is the one that we

are going to change later on in the code

let's move it below our author text

let's say layout below text author or it

was called author text let's add another

text view in here text view wrap content

and web content for its text I'm going

to save short description and let's also

give it an ID that's a txt short

description that's also move it to below

our author name let's say layout below

TX the author I think it's better to add

a margin let's say margin top I'm also

going to need two icons let's quickly

add them in our project and we'll see

why I'm adding these two so in our

driver folder we can say a new image

let's select action bar and have icons

for the icons I'm going to search for

arrow the first one I'm going to add

this one this down arrow let's change

its name to I see down arrow and also

let's change its color to a black color

let's add another one new image acid

once again this time I'm going to search

for an up arrow this one in here I think

is fine let's change its name to up

arrow by CEO arrow and let's add it into

our project now in here after this

description text I'm going to add my up

arrow so if the user decides to collapse

this current view your she would be able

to do that by clicking on our up arrow

so let's say image view graph content

and wrap content for its source let's

up arrow this one let's move it to below

our description text to X the

description and also let's move it to

the end of our card here for that we can

say alloy in finance and and we can pass

through let's give it an ID let's say DT

an up arrow okay that's it for my

expanded view now that I have defined it

I'm going to change its visibility to

gone but before that I'm going to give

an ID to this relativelayout because we

our adapter let's say ID this time I'm

going to name it expanded relativelayout

and let's change its visibility

visibility to gone also let's minimize

this relative layout so now you can see

that we have two relative layouts the

first one is the collapsed relative

layout which the user is going to see

when he or she opens our activity and if

the user clicks on the arrow that I'm

going to add in a minute we are going to

show this second relative layout

let's quickly add that arrow button so

down in here I'm going to say image view

wrap content and wrap content parse

again for the source let's say down

arrow this time I see down arrow let's

move it to below our image that's a

layout below IMG block also I'm going to

add the same margin that I added for

this text name so let's say margin top

and let's pass 70 P you can see that for

this textview we have the 70 PS back ok

let's give it an ID let's say BTN down

let's also move it to the end of our

layout online parent and let's say

through I think it's better to change

the position of name text to the

beginning of our card view now that we

have added this icon let's quickly do

that for this text view I'm going to

remove this Center horizontal attribute

I don't think we need anything else

let's switch to our adapter and let's

see how we can work on this down and up

arrow buttons before everything before I

go to my adapter I am going to open my

model my book model and I am going to

add another field so inside our package

we had a book class if you remember I'm

going to add another field in here let's

say private Bruneian let's name it is

expanded I'm not going to receive this

boolean via the constructor instead

inside the constructor initially I'm

going to set it to false so whenever we

create our book object I'm going to set

this value to false let's say is

expanded is Dakota farms let's also

create a getter and setter for this is

we are going to need them getter and

setter let's create them okay now let's

switch to our adapter class and let's

see how we can implement this logic poke

recycle every adapter first of all

inside this inner viewholder class

inside the constructor I'm going to set

an onclicklistener for that and down

arrow button but in order to have access

to that I need to initialize that in

here so let's say private image view

down arrow and pop arrow let's also

define the other UI elements for example

we had a relative layout let's say

private relative layout expanded

relative layout we had two new text

views private text view and TX the

author and txt description let's quickly

initialize them in our constructor now

that we have initialized these items I

am going to set an onclick listener for

this down arrow button let's say down

arrow that's set onclicklistener neon

click listener inside this unclick

method first of all I'm going to get the

current book that we are looking into in

previous videos we have seen how we can

get that book inside unbind view holder

method with the help of that position

but it is also possible to get it inside

this view holder class we can get it

like this we can say work let's name it

Talk is equal to our books ArrayList

that get this time for the position I

can pass get adapter position so this

way we are going to get the book that we

are currently creating a view holder for

that after getting this book we are

going to change the field that we just

defined I'm talking about that is

expanded boolean so whenever the user

clicks on this down arrow we are going

to change that is expanded field of our

book I'm going to say book dot set

expanded let's say the inverted value of

our book dot get expanded or I believe

it was is expanded instead of this line

of code in here and you can write an if

statement but I've simplified my code to

this way so basically we are inverting

the is expanded value of airport

there is just one last thing that we

need to do in here and that is to tell

the adapter that we have changed some

item in our dataset in previous videos

we have seen at this notified data set

this one but in here because I'm only

changing one item I'm going to say

notify item changed and of course in

here once again I need the position

which I can pass this get adapter

position so this way we are going to

update our recyclerview adapter later on

in our on point view holder method we

are going to take care of the expanding

and collapsing our cart view beside this

onclicklistener for this off arrow let's

quickly write that as well let's say off

arrow dot set one click listener me on

click listener and in here the logic is

the same once again we are going to

invert the value of our books is

expanded field so basically I can copy

and paste these three lines of code

let's face them in here so by clicking

on our down arrow or off arrow we are

inverting this is expanded field and

that's all we need to do inside this

view holder class let's see what do we

need to do inside on brined view holder

method so in here first of all I'm going

to check that if these expanded is true

or not let's say if Bob start get let's

pass our position but is expanded it

means that if we do need to expand our

card view then we are going to do that

and we can do that like this we can say

holder that expanded relative layout

that set visibility let's change it to

visible we also need to make our down

arrow icon invisible for that I can say

holder dot down arrow that set

set visibility let's say gone let's also

write the n space in the else case we

are going to change the visibility of

this expanded relative layout to gone

and this down arrow to visible so let's

copy these two lines of code and let's

change their values this in here is

going to work fine but if you remember I

said that we are going to also add some

sort of animation to this expanding and

for that before changing the visibility

of our UI elements I'm going to call

this transition manager I'm not sure

that if you have noticed but it's coming

from this Android extra transition make

sure to import the right one let's say

dot begin delayed transition for this

method in here we need to pass our route

in this case the route is our card view

so we can say holder dot parent if you

remember we gave an ID to our card view

which was parent and that's all we need

to do let's also do the same thing

inside the else case so by this point we

have changed the visibility of our

relative layout but also we need to set

the data for the author's name and also

for the short description I can do that

before this leaf case I can say holder

dot txt author dot set text two books

but yet let's pass position don't get

author similarly for the short

description let's run the application

expandable card view let's go to our

outputs activity you can see that right

now we are seeing the collapsed version

of our card view also the size is bigger

we also need to move this recycler view

discord view to the center of our layout

we will fix that but right now if we

click on this down arrow in here you can

see that we are seeing the expanded

version of our card we once again if we

click on this up arrow we can see the

collapsed version of our card view it

seems like our logic is working fine

let's quickly Center discord view and

also let's add another item into our

and let's see if they're collapsing and

expanding is working the same or not so

first of all I'm going to go to the

layout of my old books activity in my

app folder inside the resources layout

activity all books that XML I'm going to

change it sweets to wrap content and

also I'm going to Center it horizontally

but in here we are using this constraint

layout so for that I need to constraint

that seems better let's quickly add one

in our java file in our books activity

go to Java file down in here I'm going

to add another book I'm going to cut the

process of adding a new book okay now

that I've added another book let's

quickly run the application and let's

see if our expandable card view is

working the same let's go to our books

activity this time you can see that we

are seeing two books if I click on the

down arrow of the first one you can see

that we are seeing the short description

and also the author name but the second

book is still in the collapsed version

we can do that for the second book as

well let's quickly change the linear

layout manager to a grid layout manager

and show the problem with grid layout

manager so in here we need to pass a

column number which I'm going to fast

too let's run the application once again

so in here we have two books in our

layout file in our recycler view if I

click on this down arrow which you can

hardly see we can see that the layout

file for both of these card views

changed so this way of implementing an

expandable card view is not going to

work for our grid layout manager for

implementing the expanded court view in

our grid layout manager we need to know

a bit more about the circular views for

example we need to know that in

recyclable adapter we can have multiple

view holder classes and handling two

different view holders in recycler view

adapter is out of the scope of this

section we will cover that later on in

the course but for now we are just going

to stay with a linear layout manager our

work with expandable card views are not

done yet later on in the course we will

add some action to this expandable view

for example some buttons to delete this

book from a specific list in our

application but for now I think that's

enough and also I think that's enough

for this video in the next video we are

going to create our book activity in

which if we click on one of these card

views instead of showing this toast

message we are going to navigate the

user to another activity in order to

show some more detail about our book and

also beside in a showing more details we

to give the user some options for

example to add book to some of the lists

okay see you in the next video

in this video we are going to create a

book activity and we are going to

navigate the user when he or she clicks

on one of our books in our recyclerview

for that in my package I can right click

once again by selecting new empty

activity I can create my activity let's

name this one book activity I am going

to generate a layout file so I'm going

to leave this checkbox checked

let's close this drama file and let's

start working on our layout so our

layout is right now a constraint layout

first of all I'm going to add an image

viewing here for the image of my book

for the sample data let's select an

avatar after that I'm going to add four

buttons in here we will talk about the

purpose of these buttons for now let's

just add them after that I'm going to

add some text views in here for the name

author and description of my book I'm

going to give some ID to these UI

elements and beside that I'm going to

set some initial data for them because

we have done this before I'm going to

record the process of doing that I've

added the initial data for each one of

these items plus I gave them some ID you

can see the ID for example for this

first button which is a bt an add to

currently reading list so basically by

clicking on this button I'm going to add

this book to the currently reading list

it means that I'm currently reading it

you can guess the others this is for

adding to the visual is this is for the

books that I already read and the last

one is for adding two favorite books

also down in here we can see the books

name books author books pages and also

the books description and this image is

going to be the image of our book okay

now let's quickly add some constraints

for this one I am going to constraint it

to top of my screen and also to the left

of my screen beside that I'm going to

add a vertical guideline in here that's

right click amperes add vertical

guideline and let's move it to somewhere

around here and let's constraint our

I think 50 would be fine let's quickly

constraint our buttons for this one I'm

going to constraint it to top let's say

15 as the margin top or 50 let's quickly

constraint it to the edge of our screen

and also this vertical guideline I'm

going to do the same thing for my

buttons for the other buttons just for

the margin top I think I'm going to stay

with 24 let's add a horizontal guideline

and let's constraint our text views to

that horizontal guideline so let's say

add horizontal guideline let's move it

to down below somewhere around here

let's also add another vertical

guideline we will see its usage in a

minute add vertical guideline

I think it's place is fine and I'm going

to constraint these text views to this

guideline in here let's do the same

thing for the other text views

also I'm going to add another vertical

guideline let's say add vertical point

let's move this vertical guideline to

somewhere around here and let's

constraint these three texts to this

vertical guideline you can see that

guidelines are extremely useful when you

are designing your layout files with

constraint layout for the top of this

text view I'm going to constraint it to

the top of my book name also the same

thing for the button you can also use

the baseline but in here I've used the

top and bottom constraints okay I think

that's all of the constraints that I

need I just want to change the width and

height of this image view to somewhere

around 150 DP because different books

can have different widths and height

okay now let's quickly initialize all of

these items in our Java file let's

switch to report activity that's Java

file and let's initialize that I'm going

as you can see I've initialized all of

my UI elements now it's time to set some

values for each one of these books for

now I'm just going to create a simple

plug-in here and after that depending on

the books value I'm going to change the

value of all of these UI elements but we

shouldn't do it this way because we are

going to change the values of these UI

elements depending on the item that we

click on our recyclerview we will see

that how we can get item that we have

clicked on later on but in here just to

test our UI I'm going to create a book I

think I have a book in my old books

activity so I'm going to copy it from

there after creating this book I'm going

to create another method let's name it

set data also I'm going to pass my book

object to this method let's quickly

create this method let's say private

void set data and let's receive a book

before I do anything inside this method

I am going to add a to doing here so

that we don't forget to get the incoming

data from the recycler view okay inside

the set data method I'm going to say txd

botany that set text let's say book that

get me and similarly for the other three

text views for these pages in here

because we have set the pages as an

integer in our book model we need to

cast it into a string in here and here

is how we can do that I can say a string

with capital S dot value of let's say

book dot pages or that get pages this

way we can cast this integer to a string

and after that we can pass it to this

set text method for the description

let's do the same let's say that's a

text book that get knowing description

let's also show our image I'm going to

use glide collide that with this is an

activity so I'm going to pass this as

bitmap dot load book that image URL or

get image URL dot into our pot image so

this way we can set the data in our you

elements in order to test this

application I'm going to go to my

recyclerview adapter and from there I'm

going to create an intent so right now

inside this folder that parents

onclicklistener we are sharing a toast

message and let's remove this toast

message and let's create an intent

intent is the call to mere intent for

the context in here if you remember we

are receiving a context where the

constructor of this class so I can use

that I'm going to say M context for the

destination that's a book activity dot

class after that usually if we were

inside an activity we could have used a

start activity method but in here you

can see that we don't have that option

because this start activity method is

specific to activities if I want to use

that I can say M context dot start

activity so with the help of our context

we can have this start activity method

and after that we need to pass our

intent so right now no matter on what

book we click we are going to navigate

to book activity and in there we are

going to show the details of this 1q84

book I'm doing this because I'm going to

test my UI let's run the application and

let's see if everything works fine let's

go to our all books activity and in here

if we click on this book for example you

can see that we are seeing the details

of this book but right now our layout

has some problems for example we need to

increase the width of our buttons

because they don't fit in one line right

now and also I'm going to increase the

size of this image view let's quickly

fix these two issues in our activity

book if I click on this book image I'm

going to change this font this width and

height to 200 T P answer for these

buttons let's increase the beats from

150 to I believe 170 would be fine let's

run the application one more time and

once again let's go to our book activity

this time it's somehow better also we

need to be careful about this long

because if this description don't fit on

the screen and be probably and I

that I'm going to add a scrollview into

my layout fight we haven't seen a

scrollview but its purpose is to create

a view that we can scroll let's quickly

see how we can add that in our

constraint layout so basically what I'm

going to do is that I'm going to change

these parents to a relative layout after

that I'm going to create a scroll view

inside that scroll view I'm going to

create a constraint layout and I'm going

to move all of these items into that

constraint layout let's see what I'm

so as I said I'm going to create a

scroll view for the width and height

let's say match parent inside this

scroll view I'm going to create a

constraint layout once again for the

vision height let's say match parent

after that I'm going to move all of my

elements to inside this constraint

layout and after everything I'm going to

change this constraint layer to a

relative layout so let's select all of

these items and after everything as I

said let's change the parent to a

relative layer let's enable the split

view and let's see if we have a good

layout it seems like we have done a good

job let's run our application let's go

to our book activity and we can see the

same result let's quickly add a longer

description and that's if you can scroll

our view I've copied the text in my book

activity I'm going to set that text as

the long description of this book but

before that I'm going to create a string

in here let's say long description is

equal to this text that I'm going to

now that we have this text let's set it

as the long description of our book

let's run the application once again and

let's see if we can scroll our view

let's go to block activity and in here

you can see that you have a long

description that does not fit on our

screen but as you can see we can scroll

this view ok I think that's enough for

this video this was a short video just

to create a layout file for our book

activity in the next video we will see

that how we can pass our book from our

recycler view to this activity and

beside that we will work on the logic of

these buttons see you in the next video

in this video we are going to write the

logic for these buttons we are going to

add our books two different categories

by clicking on each one of these buttons

but before I do that I need a data

storage to save these books to different

lists in a normal application in this

situation you may want to use a database

a database is a place that you persist

your data it can be a local database on

your smart phone or it can be an online

database on a web server in here we

haven't talked about any of those we

haven't talked about databases yet we

are going to talk about them later on in

the course in fact we have a section

dedicated to databases but in here we

are going to use an alternative we are

going to use some of the capabilities of

java language in previous videos in java

section if you remember I talked about a

static keyword I said that when you

define a variable or an object as a

static that variable will have the same

value in all of your application

regardless of where you have initialized

it in here we are going to take

advantage of that and we are going to

define our different lists of books as

static variables this way we have the

same lists when we are working with our

application in different activities but

there is a downside to this way of using

a static values your data would not be

persisted it means that if you close

your application you lose all of your

data at the end of this section I will

introduce another alternative in which

you can use to produce your data but in

here for now let's just use a static

variables for that I am going to create

a utility class in my package and we

will see in action why I am creating

this class so in my package let's

right-click new Java class I'm going to

name it utils in a real world

application this utils class is probably

your database class but of course the

name should be different but in here we

are not using databases so I named it

utils the first thing that I'm going to

do inside this class is that

to make this class Singleton so I'm

going to implement singleton pattern in

here inside this class if you remember

from the Java section whenever we

implement a singleton pattern for a

class we can have only one instance of

that class in our entire application I'm

making this class singleton because I

want only one instance of this class

basically this is the class that we are

going to interact with our aesthetic

and for that I am going to be sure that

I have only one instance of this class

ok let's quickly see how we can

implement singleton pattern first of all

I'm going to create a constructor for

this class it's an empty constructor and

right now we don't have anything after

that I am going to define a static

instance of this class let's say private

a static utils the type of our class

let's name it instance beside that I'm

going to need a getter for this instance

you remember all of these from the Java

section so I'm not explaining them let's

say getter for the instance first thing

I am going to change the modifier of

this constructor to a private let's do

that and inside this get instance method

I am going to write the logic to make

this class a singleton so I'm going to

say if now is not equal to my instance

then return the instance but in the else

case in case if the instance is now

let's say instance is equal to new you

tools and after that we can return our

instance let's say I return the instance

because we are returning in each one of

these cases we no longer need this

returned instance down in here in the

Java section we also have used the

synchronized keyboard if you remember we

in there I said that the synchronized

keyboard will make your method to be

thread safe it means that if different

threads at the same time call this

method this synchronized the keyboard

will cause them to call this method one

by one and not at the same time but in

this application we are not going to use

threading we are going to have only one

thread called the main thread so for

that I'm not worried about trading issue

in here and I can safely delete this

synchronized keyboard so by now this

utils class is a singleton class now we

can create our aesthetic lists so for

example in here I can say private static

let's say ArrayList of different books

let's call this phone all books as you

can guess this one is going to represent

all of our books in our application but

where do we initialize this all books

ArrayList we know for sure that when we

create an instance of our utyos' class

we are going to call this constructor so

the perfect place to initialize these

all books ArrayList is inside this

constructor let's move it to down below

this all book so that we can follow the

logic better and inside this constructor

let's say if null is not equal to our

we don't want to reinitialize our

ArrayList we just want to initialize it

one time when we create our application

or better than that would be to say if

null is equal to our old books I'm going

to say all books is equal to new

ArrayList and after that I'm going to

create another method in order to add

some initial data to this all books

ArrayList so let's say in its data let's

go to create this method by pressing Alt

+ Enter you can create your method for

now I'm just going to add a to doing

here and later on we will complete this

method let's say add initial data in

case if you have forgot about these two

do's and these are some sort of comments

that you live for yourself or for your

colleagues so that we don't forget

anything later on and when you want to

go in production you can check these two

and you can see the works that you left

for the future okay let's move on from

this part beside all books are released

I'm also going to define other ArrayList

let's say private a static array list of

different book let's name it already

read book let's define three more

one for currently reading books one for

one to reading books or wish list books

and another one for favorite books

similar to our old books aerialist we

need to initialize this ArrayList inside

our constructor as well so down in here

once again I can say if null is equal to

my already read books then I'm going to

initialize it let's say already read

books is equal to new ArrayList but I'm

not going to add any initial data

because we are going to leave that

option for the user later on when he or

she uses the application let's do the

same thing for the other three array

we now have initialized all of our lists

now let's see how we can get the values

or the items from our lists for that I'm

going to create get our methods for

example for this all books I released if

you want you can create a getter let's

quickly create that down in here by

pressing Alt + insert you can create

getters for all of your lists let's add

some initial data to our all books

ArrayList and that's an test this UTS

class and let's see if everything works

fine so if you remember in all box

activity we have created this array list

manually after that we have passed these

energies to our recyclerview adapter I'm

going to cut the initializing of our

array list from here and I'm going to

move it to my utils class right now we

have an error we will fix that so inside

utils class inside this in its data

method after this to do I'm going to

paste my ArrayList this time instead of

saying books that add which is this

array list I'm going to say all books

that add this one in here so this way we

are adding two books to our all books

ArrayList I can safely delete this one

as well remember that we are calling

this init data method from inside our

constructor when we are creating our all

so whenever we run our application and

we call this utils class this utils that

get instance method we have some data in

our all books ArrayList now that we have

some data in our all books activity

instead of these books we can say utils

with this capsule you don't get instance

if you run our application if everything

inside our util class works fine we

should see two books in our all books

activity let's quickly test that if we

go to our all books activity you can see

that we are seeing two books it seems

like our users class is working fine we

ton of more codes inside this UTS class

but more on that later on for now let's

see how we can pass a book from our

recyclerview adapter to the book

activity for example right now if I

click on this the myth of sisyphus you

can see that we are seeing this 1q84 it

means that we didn't pass our book to

this book activity in fact in our book

activity we are defining the book itself

and we are not getting any data from the

recyclerview let's see how we can pass a

book from our recyclerview to this book

activity so if you remember inside the

book recyclerview adapter inside this

holder dot parent thoughts at

onclicklistener inside the onclick

method we have created this intent the

use of this intent is to navigate the

user to the book activity the good thing

is that with this intent you can also

pass some sort of data let's quickly see

that as well so for example in here I

can say intent dot put extra you can see

that we have a ton of these different

methods for all sort of variables and

all sorts of data let's use one of them

for example I can pass the book ID in

here you can see that in here we need

two arguments a string and after that

data that we want the string is always

the key or the name of your value in

here for example if I say book ID later

on inside my book activity with this

book ID I can get the book ID so the

values inside your intents are key value

pairs for the idea of this book I can

use this books I release that we have

inside this adapter I can say books that

get let's pass position let's say target

ID so this way we are passing the ID of

our book - the book activity later on in

our book activity we will get our book

by its ID if you remember I said that

the ID for each book is going to be

unique it's worth mentioning that you

can also pass the book itself you can

that instead of passing an integer we

can pass a course a little bit let's

quickly see that you can say intents

that put extra and then in here if you

take a look one of the arguments in here

is this part of the bill we will talk

about cars available later on in the

course but basically it's an interface

that we will not serialize your class at

the time of transferring it from one

activity to another activity and at the

deserialize your object don't worry

about these two words that I am using

basically using parsable is really easy

we will take a look at that later on in

the course but for now we are just going

to pass an integer beside that you can

also set multiple extras for your intent

for example if I want to pass the book

name in here once again I can say that

put extra for the key I'm going to say

for the name and if I want I can say

oops that get position do not get me of

course we are not going to need this in

here but I just wanted to say that you

can pass multiple extras with your

intent okay now that we are passing some

data with our intent how we can retrieve

that data in our book activity before

that let's quickly remove this one to

have a reviewing here first of all we

are creating our intent the context is

this M context which we are receiving

with the constructor of this adapter the

destination of this intent is book

activity dot class we are calling this

pot extra method on our intent and with

that we are passing some integer in this

case we are passing the book ID after

that with the help of our context we are

starting to activity which in this case

is this pub activity dot class so now we

can continue our code from inside the

book activity inside on create method

let's close this one also I'm going to

close this one utils class my layout

file and let's open book activity

so inside this on create method in here

if you remember we are creating a book

and we are setting its value to our UI

elements you can see that we also have a

to-do in here get the data from circular

view in here so if we want to get the

data in this case the book ID from our

recyclerview we can say something like

this we can say intent let's call it

intent is equal to this time instead of

saying new intent I can say get intent

so if you use this get intent method you

are going to receive the incoming intent

the intent that caused this activity to

be launched but you also need to be

careful about non values of this intent

because this intent can be null at some

times so for that I can say if null is

not equal to my intent I'm going to

continue in here after that I'm going to

receive the book ID I'm going to say int

book ID is equal to intent dot get int

extra you can see that we have a lot of

this get extras method for different

kind of data for example if you are

going to get an integer we can call this

get into extra we can see that the

method in here is waiting for two things

you can press down the control key and

you can see the documentation first of

all we need the name of our variable

which if you remember was book ID and

the second one is a default value so in

case if for any reason this get into

extra wouldn't be able to get any data

from our intent we are going to assign a

default value for the name let's pass

pop ID and for the default value I'm

going to pass negative one because I

know for sure that and none of my books

in my list are going to have negative

one as their ID also about this name

this key t spoke ID in here you need to

be extra careful about this the

characters the upper cases and their

cases need to be exactly the same if you

put anything wrong in here you are not

going to retrieve your data there is a

better option than hard-coding your keys

passing your kids manually you can

create constants for example above in

here I can say public static final

string the convention is to name your

constants in upper cases for example in

here I can say book ID key I can also

assign a value to this one for example I

can say book ID now that I have defined

this constant in here I can pass it in

two places for example the first time I

can pass it as a key I can say book ID

key and also inside my adapter class

instead of hard-coding the key in here I

you can see that we need to import this

by pressing Alt + insert we can import

this constant into our class if you take

a look at above in here in the imports

we are importing this constant into this

class so this way by using different

constants you make sure that the keys

are the same in two different places

okay let's switch back to our book

activity so by this time after this line

of code we either have a negative one

value or we have the book ID we need to

create an if statement for this negative

one value let's say if our work ID is

equal to negative one or the better

logic would be - if it's not equal to

negative one let's pursue the code so by

this time inside this if statement we

have our plot ID how do we get the POC

by its ID if you remember at the

beginning of this video I said that we

interactions with our lists inside the

UTS class so for that once again I'm

going to go to my utils class I'm

pressing double shift in order to pop up

this search menu if you are wondering

anywhere in Android studio you can press

shift two times and you can get this

menu in which you can easily type and go

to your class for example inside this

utils class after everything I'm going

to create a method I'm going to say

public book is going to be the return

type of this method let's say get book

by ID we also need to get the ID let's

say int ID after that inside this method

I'm going to login to my all books

activity and I'm going to return the pot

by its ID for that I'm going to create a

for loop for each loop to be precise

let's say for book be inside our all

books are released in case if B dot get

ID with equal to the ID that we received

then we are going to return B

so if we have a book with this idea we

are going to return it but after the

four do if we didn't return anything we

are going to return now by returning

null in here we are acknowledging that

we may not found a book with this ID in

our list so whenever we call this get

put by ID method we also need to be

careful about the null values because

the result can be known for example

inside the pot activity in here I'm

going to say book let's name it

incoming work is equal to our utils

class that get instance first of all dot

let's say get book by ID after that we

can pass our book ID after this line of

code we need to make sure that this

incoming book is not known so let's say

if null is not equal to our incoming

book then we can call our set data

method which is this method I can

account this and I can paste it inside

this if statement you can see that

before getting our book and before

passing it to this set data method we

are doing three security checks first of

all we are checking that our intent is

not now after that we are making sure

that we have received some data from our

after that we are checking that if we

have such a book with this ID in our

list in a normal scenario in a good

situation none of this would be

necessary and you can simply call these

get books by ID method and you can get

your book but a lot of things can happen

when you call your activity and when you

pass your data your activity may be

destroyed your activity may be

interrupted by some call that user

receives your activity also may be

called from different places and also

for other security reasons you always

need to check for the intent for the

incoming data and for the data itself

inside your data storage sorry I need to

change this book to incoming booking

in there okay now that we are setting

our incoming book we can safely delete

the spot above in here let's comment all

of this let's test our application and

let's see if we can successfully

navigate the user to book activity and

show the appropriate book let's go to

all books activity 1q84 we are saying

1q84 if we click on the myth of sisyphus

you can see that now we are seeing the

meetups is the first it seems like we

are passing the data from our recycler

view from inside the all books activity

to the bot activity successfully okay I

think that's enough for this video I did

want to talk about the logic for these

buttons but I think that's better to be

left off for the next video okay see you

going to take care of these buttons we

are going to add the book to different

lists by clicking on each one of these

buttons beside that we are going to

disable the button if the book already

exists in one of these lists for example

if the book exists in the users wish

list we are going to disable this one to

read button let's go to book activity

and let's see how we can do that so

inside this book activity insight is on

create method I am going to call another

method but I am going to do that inside

this if statement after I made sure that

I have an incoming book so let's name

this method and a handle already read

I'm also going to pass the incoming book

itself let's quickly create this method

down in here let's say private void and

let's also receive a book inside this

method first of all I'm going to check

that if this incoming book exists in our

already read books so for that I'm going

to say ArrayList of book let's name it

is equal to you Till's not get instance

this method after that I'm going to

create a for each loop let's say for

book be inside our already read books

also before this for loop I'm going to

define a boolean and its purpose will be

so that's a boolean let's name it exist

let's initialize it to false down in

here inside the for-loop I'm going to

say that if B that get ID is equal to

our incoming pour target ID if that's

the case we are going to change the

value of this boolean let's say exists

in already read books is equal to true

so after this for loop we know that if

the pop exist in our already read books

ArrayList and we can use this program we

can say if existing already read books

is equal to true then we are going to

disable our button because we don't want

to add this book one more time in the

already read books ArrayList so let's

say BTN already read or between add to

already read that set enabled this

method and let's pass false so this way

we can disable a button in the else case

I'm going to set an onclicklistener for

this button and I'm going to add it to

my already read books ArrayList so let's

say B thean add to already read that set

onclicklistener and inside this onclick

method we need to add it to our list but

because I'm going to keep all of my

interactions to my lists inside the

utils class I'm going to create that

method inside the utils class so let's

go to utils class and let's minimize all

the extra unnecessary method for now

down in here I'm going to say public for

the return type of this method I am

going to say boolean and we will see why

public boolean bad to already read let's

also receive a book and inside this

method let's say return already read

list already read books dot add and

let's pass our book so if you remember

from the Java section when we use this

add method on our ArrayList this add

method is going to return a boolean the

boolean is going to be the indicator

that if we have added the book

if you first down the control key or if

you are on a Mac system if you press

down the command key by clicking on this

ad you can see the documentation in here

you can see that if we successfully add

this element which is the generic data

type in Java at the end of this method

we are returning true it means that we

have added elements into our an

ArrayList successfully so in here we are

returning death boolean electron in our

book activity we are going to check for

this boolean and we are going to make

sure that we have added this block item

into our list successfully that's all we

need to do inside this ad to already

read and we can switch back to our book

activity so once again inside this

onclick method of this BTN add to

already read we are going to check that

if you teams target instance dot add to

already read with the incoming book if

that's true we are going to show a toast

message let's draw a book added but in

the else case I am going to show a

different toast message let's just say

something wrong happened try one more

also in the if case in case if we add

the book successfully I'm going to

navigate the user to another activity to

be precise I am going to create an

activity called already read books and

in that activity we are going to show

the list of books that the user has

already read but first of all I need to

create that activity in here I'm just

going to put a to do right now so let's

say navigate the user once again let's

review what we are doing inside this

method first of all we are getting there

already read books from this utils class

after that we are checking that if our

book exists inside this already read

books if it does we are disabling our

button but if it doesn't we are setting

an onclicklistener for this button in

which by clicking on that button we are

adding the book to already read books

ArrayList if that process goes well we

are going to show a toast message and

after that we are going to navigate the

user to already read book activity but

in case if something wrong happens we

are just going to show a toast message

this else case would never happen but I

just put it for the security reason we

don't want to gamble on anything that

can happen in our application ok by now

application and check if we can

successfully add a book to our already

read book ArrayList let's run the

application let's go to our book

activity by clicking on one of these

books and in here you can see that this

button is not disabled and that's

because this book does not exist in our

already read book ArrayList if we click

on this already read button you can see

that the book has been added to our

ArrayList successfully I said that after

this we need to navigate the user to

already read book activity but for now

let's go back to levels and once again

let's go to our book activity and let's

see if that button is still available

which is not it seems like we have wrote

the logic perfectly ok now let's quickly

create the already read book activity

and let's navigate the user there

but before that I'm just going to warn

you about something I don't usually

comment my coat and that's because I'm

lazy I had that son execuse but you

don't follow this behavior you put

comments wherever you feel necessary in

your code for example before the

declaration of this method we can put a

comment and in here we can specify the

purpose of this method for example I'm

going to say enable and disable button

besides that we are going to add the

using comments in your code might seem

some minor thing but believe me if you

come back to your code one month later

probably you don't remember any aspect

of your code and only thing that you

have that will help you to understand

your code are these comments also beside

that you may work with a team on a

project and these comments can be

so not only at the declaration of your

methods but wherever else you feel like

you need comments please do use comments

ok let's move on from this part and

let's create our already read book

activity so in my project I can right

click on the package and by saying new

activity empty activity we can create

our activity I'm going to name this one

to generate the layout fine so let's

leave this checkbox and I checked the

layout file for this activity is going

to be really simple basically we just

need a recycler view in that recycler

view we are going to show our books so

let's switch to our layout file and

let's drag a recycler view in our layout

for the vid some height I am going to

say match parent and also let's give it

an ID I'm going to say pork recycle of

you beside that let's add some margin in

our split view I believe that would be

better let's add a margin in here margin

I believe that NDP would be fine okay

now back in our Java file we can

initialize our recycle view for example

down in here I'm going to say recycler

view let's name it recycler view is

equal to find view by ID our that ID

that books recycle view I don't think we

had s let's remove that so that we don't

get a nullpointerexception after that

I'm going to create my adapter and here

is where the recycler view is coming

very handy we have created a book

recycler view adapter in our project

previously and the good thing is that we

can reuse our adapter as many times as

we want so once we have used that in our

all books activity we can also use it in

here for example I can say box recycler

view adapter let's name it adapter is

equal to new box recycler view adapter

we also needed a context let's pass this

let's say recycler view touch set

adapter and let's pass our adapter

beside that we can set a layout manager

for our recycler view I'm going to say

recycler view that set layout manager

once again I'm going to pass linear

layout manager let's pass our context

for the data I am going to say adapter

set box I'm going to pass newton's

target instance that get already read

this method in here also we are keep

seeing this highlighting here please

highlight says that you can also use

this get already red box method without

instantiating your UTS class let's do

that we can do this because this get

already red box method is a static

method so for example before getting an

instance I can say that get already red

box you can see that it's working

but there is a potential bug in here

right now the first place that we are

calling our greetings class is inside

the all Box activity I'm talking about

that UTS that get instance method so

before that we don't have any instance

of this utils class in our application

so before going to add all Box activity

we don't have any ArrayList called

already red box because if you remember

we are initializing our array lists

inside the constructor of this utils

class what happens if the user decides

to come to this already read books

activity first and don't go to the out

box activity I mean that hits this gate

already red box method is going to

return null and that's where the

potential bug can happen inside the

adapter of our recycle of view we are

calling some functions on our books

ArrayList and we know that calling a

function on a null reference can cause

null pointer exceptions what can we do

to avoid this now enter exception we can

call youtube's target instance inside

the main activity we don't meet any

functionalities from UTS class in main

activity but we are just going to do

that in order to avoid null pointer

exceptions and to initialize all of our

lists so let's go to main activity and

initializing all of our buttons I'm

going to say utils target instance this

way we are calling the constructor of

this utils class and we are initializing

our lists also now that we are here

let's quickly set an onclicklistener for

this beauty and already read I'm going

to say BTN already read that's at

onclicklistener me onclick listener and

the user to this activity to already

read books activity so let's create an

intent intent is equal to new intent for

the context let's pass main activity

that this and for the destination

already read book activity third class

after that we can say start activity and

we can pass our intent there is one more

place that we need to navigate the user

to already read books activity and

that's where we have added the book into

our already read books list let's copy

this intent and let's go to our book

activity if you remember we had a to-do

somewhere down in here in which we are

saying to navigate the user after this

to do I'm going to paste my intent but

of course I need to change this context

let's change it to this or because we

are inside this interface we need to

pass book activity that this now that we

are navigating the user we no longer

need these to do let's remove that and

let's run our application once again and

let's see if everything works perfect

first of all let's go to already read

books activity we can see that right now

it's empty it's also better to show

something in case if we don't have

anything in our list we will take care

of that in future videos but for now

let's go back and let's go to our book

you can see that this already red box

button is enabled you may be wondering

why this one is enabled because

previously we have added this book into

our already read books ArrayList well

that's because we are not persisting our

data we are not using any database or

anything we are just simply using a

static array lists because of that the

life of our data storage is only

whenever we close our application in

future videos in this section we will

use another option to persist our data

but for now we just lose our data

whenever we close our application

ok let's click on this already red pop

successfully navigating the user to

already read book activity if we go back

we are once again inside the book

activity but still this already red

button is enabled this is because of an

entirely new concept that's because of

the activity lifecycle whenever we add

this book to our already read book list

and we navigate the user to already read

book activity and from there when we

press this back button we are not

calling the oncreate method of our

activity we are calling some other

methods in which we are going to talk

about them in future videos in activity

and fragment section so we are not going

to talk about this problem right now but

if we press this back button once again

and if we go to our book activity you

can see that now it is already read and

button is disabled but the thing that we

are going to talk about in here is that

whenever we add a book to our already

read book I released and whenever we

navigate the user to and already read

book activity by pressing this back

button we are going to navigate the user

back to the main activity and not this

pop activity we are going to talk about

how we can fix that for example if I go

back and add this other book to my

already read book array list let's

quickly do that whenever we are

navigated to this already read book

activity by pressing this back button we

are going to navigate the user back to

main activity and not to the book

activity we will talk about that

later on let's also go back to main

activity and from there let's click on

this already read books once again you

can see that we have two books in our

already read books ArrayList there is

just one minor problem in here and that

we need to Center our recycler we will

fix that ok let's fix these problems one

by one first of all let's enter this

recyclerview and after that let's take

care of this back button so for this

recycler view I can go to my layout file

activity already read book and in here I

can change the width and height to wrap

content and after that I can constraint

my recycle review because we are inside

a constraint layout or I think this

button constraint wouldn't be necessary

okay it seems like fix this let's go to

our already read book activity that Java

fine and let's see how we can take care

of the black button for the back button

we have few options the easiest one is

to override some method called on back

pressed if you press ctrl o somewhere

inside your activity if you search for

on back pressed we can see this method

in here we are going to override this

method this method is going to be

triggered whenever the user click on the

back button so inside this method

instead of the super statement we can

simply create an intent and navigate the

user back to main activity let's see how

we can do that we can say intent intent

is equal to new intent let's pass this

as the context and main activity that

class as the destination after that

let's say start activity and let's pass

let's run the application and let's see

if we are going to navigate the user

successfully back to main activity let's

add one book to our already read books

are in list for example this one we are

navigating the user to already read book

activity if we press back you can see

that now we are inside the main activity

but there is one more problem in here if

you press this back button we will be

navigated back to already read books

activity and that's because of something

called back snack in programming so

whenever you are going to an activity

some snack will be added to your

application basically the hundred system

is going to keep a history of where the

user visits in your application whenever

you go to a new activity in you a stack

or to be personalized a new task will be

added to your back stack you can deal

with that back stack if you want for

example you can clear that back a stack

or whenever you are defining a new job

for example whenever you are firing an

intent we can say that this is an

entirely new task and you don't want to

visit in your application in order to

define your intent as a new task you can

add some flags to your intent for

example after defining your intent you

can say intent set flags this method in

here and you can pass two flags you can

say intent dot let's say clear task you

can see this flag activity clear tasks

in here and also I'm going to add one

more flag you can add one more by using

this pipeline let's say intent dot new

task you have this flag activity new

task so by using these two flags on your

intent you are saying that we want to

clear your back stack and also you are

defining this intent as a new task so

now if we run our application if we add

a book to our already read books

ArrayList for example this one now if I

press this back button I will be

navigated to the main activity but my

back slack is now clear it means that if

I press this back button we are going to

quit the application so this way by

using these flags and you can define a

new task ok let's move on from this part

and let's work on the other buttons in

our POC activity if you remember we had

three more buttons so once again I'm

going to go to the uncreate method after

getting the incoming book I'm going to

call another method called handle one to

once again I am going to pass my

incoming book the logic for this button

and the other two buttons are going to

be exactly the same so I'm going to call

two more methods in here hand our

currently reading book and handle

let's quickly create these methods

the logic from inside this method let's

copy them and we will change them if it

was necessary I'm going to copy this

whole method and I'm going to paste it

inside this handle one two reports we

need to change if you think first of all

we need to make this book final because

we are using it inside this onclick

listener after that I'm going to change

the name of this already read books

ArrayList I'm not sure if I talked about

this previously but basically whenever

you want to change the name of a

variable or some object in your

application that you are using in

multiple places you can press Shift + f6

and in here you can refactor the name of

your variable for example in here I am

going to save one to read books you can

see that when I change the name of this

array list it will be changed in all of

its usages so let's say I want to read

I also need to change this method in

here let's say get one to read books I

need to change the name of this boolean

after that I need to disable another

button beaten add to one to read this

onclicklistener for this with an ativan

to read so let's change that I also need

to create another method inside my UTS

class so that I add this book to my

wishlist so let's go to utils and then

in here let's create a similar method

you can see that the method is basically

the same we are returning a boolean once

again and we are adding the book into

our bond to read books ArrayList now

inside our book activity instead of this

add to already read book I can say add

to want to read there is just one more

thing that I need to take care in here

and that's navigating the user to want

to read books activity and not already

read book activity so let's quickly

create that other activity once again in

our package we can say new activity

the layout file is going to be exactly

the same so I'm going to fast forward

the process of adding the recyclerview

don't worry if you need to check the

source code I will upload the source

code at the end of every video but

basically these are and just copy and

pasting okay let's switch back to our

one to report activity and let's

initialize our recycling once again I

think I can copy some of the logic from

the already read web activity let's copy

but this time instead of this get

already read books I'm going to say get

one to read works this one let's also

take care of the back stack I'm going to

copy this whole method from the already

read pot activity you may be wondering

why I am copying and pasting why I have

created four different lists later on we

will see some minor differences between

these four different lists okay now that

we have created this activity let's

navigate the user to want to read

activity from inside our POC activity

that all we need to do inside this

handle want to read box method let's

quickly create the other tool in order

to save your time because it files just

copy and pasting I cut a part that I

wrote these two methods but let's

quickly take a look at them so first of

all this handle favorite books you can

see that the book is final we are

getting the ArrayList we are checking

that this book exists in our favorite

books after that if it does exist we are

going to deactivate our button but if it

onclicklistener if adding the book into

our favorites ArrayList is successful we

are showing a toast message and we are

navigating the user to favorite activity

I have ensured that in a minute but in

case if something wrong happens we are

sharing a toast message just like we did

for already read books beside that and

the same thing happens inside this

handle currently reading book you can

see that basically the logic is the same

we just changed the name also beside

that I've added two more methods inside

my utils class this add two currently

reading book and add to favorite once

again you can see that we are returning

a boolean beside that I've created two

new activities this currently reading

activity which once again we are

initializing every circle view and it's

adapter and we are setting the data in

our adapter by using utils that that

method that we have in our utils class

we are also taking care of this unpack

first button beside that we have created

this favorite activity which you can see

the code is a lot like each other

and also for the layout fonts for these

two activities if you take a look at

them I only have a recyclerview in each

one of them I just caught the process to

save your time but if you want to check

the source code please do that I will

upload the source code at the end of

every video in this section on the links

that you can see on the screen so feel

free to check that if you need but in

here let's quickly run our application

and let's see if everything works fine

let's go to our block activity and let's

add this book to one of our array lists

for example let's add this one to our

favorites the book has been added we are

navigating to the favorite activity if

you press this back button we are

navigating back to the main activity

let's see our favorites from here

but I didn't set down quick listeners

for these buttons I will do that let's

see our books once again and let's add

this 1q84 to our I don't know currently

reading books it seems like we have

okay I think that's enough for this

video in the next video we are going to

work on showing our card views I'm

talking about this book card view

differently in different activities so

for example inside this all books

activity we can see this card view we

can expand that in different lists for

example inside the favorite books list

we are going to add some actions for

example two text views so that by

clicking on them we remove the book from

the list we are going to show that for

the books that are inside our lists but

we are not going to show that inside all

books activity and at the same time we

are going to use only one adapter so

that's one thing that we are going to

inside that if you had time and we will

work on this about in here basically we

are going to show some dialog message

and we will see how we can show a dialog

okay see you in the next video

in this video we are going to create a

delete button in our current view

English will be available in all

activities beside the old books activity

let's see how we can implement that

functionality I'm going to add my delete

button inside this expanded version

inside the second relativelayout inside

the list item pop that XML file so if I

expand this relative layout and change

its visibility to visible for now I'm

going to add the delete button somewhere

beside this up arrow I'm going to place

it in here so for that down in here

after my image view after this bitten

off arrow I am going to say text view

wrap content and wrap content for the

width and height for the text I'm going

to say delete let's move it to below our

short description let's say layout below

and let's address our txt short

description after that I'm going to move

it to the left of this up arrow button

so let's say to start off I DBT and our

pyro let's quickly add a margin let's

say margin end and I believe 70 P would

be fine let's also change its color to a

red color let's quickly define a color

in our color resources inside this color

resources let's copy this one and let's

create a new one I'm going to change its

color to red and for its value and let's

select one of these two I'm going to

select this one but I think this one is

a pink color so let's change the color

to pink next in our list item book that

XML file in our text view I'm going to

say text color and I'm going to change

it to my pink color let's also give it

an ID I'm going to say BT and delete

beside that let's change its visibility

to argon later on in our adapter we will

change this visibility if it was

necessary okay we are almost done with

our card view let's just change the

visibility of this expanded view to gone

once again so in here I'm going to

change this one to gone and we are done

with our layout file let's go to our

adapter and let's pursue the code from

there so in our books recycle we are

if you remember inside on point

viewholder method we are checking that

if you should expand the card view or

not I'm talking about this if statement

if pops get that is expanded so inside

is if case I'm going to check that if

I'm inside all box activity or not if I

am inside the all box activity I'm not

going to show the delete button

but in other activities I am going to

show that for that I'm going to add one

more variable inside this adapter class

above in here after the context I am

going to add a string let's say private

a string I'm going to name this string

parent activity I'm going to receive

this string by the constructor so I'm

going to delete this constructor and

create it once again this time let's

select the context and this drink at the

time of initializing my recyclerview

adapter in different activities I'm

going to say that which activity is

calling this adapter for example if it's

the old books activity I'm going to pass

all work if it's others I am going to

pass the correspondent text after

receiving this string down in here

inside the unbound view holder method

I'm talking about this if case in here

I'm going to check that what that text

is so I'm going to say if parent

activity dot equals let's pass some text

in here for example let's say all books

it's better to use constants in here but

just for the sake of simplicity I'm

going to pass my text if the parent

activity that calling this adapter is

the all box activity we are going to

change the visibility of our delete text

to gone so let's say holder but I

believe we have it instantiated our

tillu text view in our view holder class

let's quickly do that so down in here

inside this view holder I'm going to

define my daily text so let's say

private text view let's name it VT and

delete and also after that inside the

constructor let's instantiate it for

example down in here I'm going to say

BTN delete is equal to item view dot

ordered ID dot retain delete now that we

have this element in our view holder

have access to it inside OnPoint

viewholder method so in our if statement

I am going to say holder dot BT and

let's icon let's write the other cases

for example let's say else if if our

parent activity is equal to already read

books if that's the case we are going to

delete this book from the already read

ArrayList instead of this if statement

you can also create a switch statement

first of all I'm going to write the

whole if statement and after that we

will write the logic for each case let's

say else if and activity that equals

let's say one to read the other case

would be as if and activity is equal to

currently reading we have one more case

let's say else the else case would be in

a favorite activity now let's write the

logic for each one of these cases for

example if it's the already read pop

onclicklistener for this bit intimate so

let's say holder that BTN delete dot set

on click listener let's say me on click

listener and inside this onclick method

I need to delete the poop from my

ArrayList once again I'm going to keep

all my interactions to my aesthetic

array lists inside the utils class so

I'm going to write another method inside

that with us class let's quickly go to

that class and down in here after

everything let's say public boolean once

again you can see that the return type

of this method is a boolean I will talk

let's say remove from already read let's

also receive a book and after that

let's return already read puts dot

remove and let's pass our book like the

add method on our ArrayList this remove

will also return a boolean if you want

you can check the documentation by

pressing down the control key and

clicking on this remove you can see the

guideline in case if we remove this item

from our array list successfully we are

returning true but otherwise we are

returning false we can use this boolean

remove the book successfully let's go

back to our adapter and in here let's

say if you teams that get instance to

add remove from already red book which

we need to pass our report by saying

boots target position if that was

successful we are going to show a toast

message let's say book removed but

instead of the book I'm going to pass

the name of the book which I can say box

that get position target name let's save

close removed also after that we need to

notify that the data set has been

changed because we want to refresh our

recyclerview so we can say notify data

set changed but in the else case let's

just show a toast message let's say

something wrong happened clear sorry

again we have write the logic for

removing a book in case if the planet

activity is already read but now that we

have changed the constructor of this

adapter probably we are going to see

some errors in our application wherever

we have instantiated this adapter we are

going to see some read errors for

example if we go to our all books

activity you can see that in here we

have an error and that's because now our

constructor needs two elements the

context and also the parent activity

which is a string for example inside

this all works activity I can say all

works let's see other places that we

have instantiated our adapter for

example already read books activity

notice that these strings should be

exactly the strings that you have passed

inside your if cases okay let's go to

currently reading activity and let's

pass one in here as well let's go to do

the same thing for the other two

ok let's close all of these extra files

and let's test our application and

that's if we can successfully to meet

the books from different activities

remember that we have written the case

only for this already read and the

others shouldn't work before I test my

application I'm going to add one more

line in here because it seems like I

have forgot something so in case if the

parent activity is already read activity

first of all we need to change the

visibility of our BTN delete I can say

holder that between delete let's say

that set visibility and let's pass

visible let's run our application let's

go to our all works activity in here if

we click on this down arrow we shouldn't

see this delete text let's try that as

you can see we cannot see any delete

that seems to be good let's go to our

activity and let's try adding this book

to our already read list it seems like

it has been added successfully if we

click on this drop down we can see that

this time we can see the delete button

let's try clicking on that it seems like

we are getting a crash let's open our

locket and let's see what the crash is

it seems like I've lost the error let's

run the application once again and let's

try everything one more time see all

boats put activity add to already read

list and let's try deleting it once

again it seems like the air is happening

online 78 of our recyclerview adapter

yes the problem is that first of all we

are removing this book from our list and

after that we are trying to get the book

from our list for that we are getting an

index out-of-band exception because this

book no longer exists in our books

ArrayList what I can do is that I can

save the name of book before this button

before this include listener or

alternatively in here I'm just going to

say port removed but still it is and in

here let's say broke removed let's try

running the application one more time

and let's see if you still see the

exception all box activity book activity

to already read list this time let's try

to leting this book it seems like we

have removed the book successfully also

we have refreshed our recycler

this empty screen is not a good user

experience we probably should show some

text message in case if we don't have

any book in our list we will fix that

later on in future videos but for now

let's go back I also don't like this

behavior that we are instantly removing

the book for example in here if we try

to add a book the user might press this

delete unwanted leaf for example by

accident before deleting the book we

also need to get some confirmation from

the user I think that creates a better

user experience so in here after

clicking on this delete button I'm going

to show a dialog message to the user and

I'm going to ask that if he or she is

sure of deleting this book let's see how

we can create a dialog so in here before

I'm going to delete this whole if

statement and here is how you can create

the simplest alert dialog you can say

alert dialog this one that comes from

and with x-dot app compat let's say that

builder let's name this builder is equal

to new other dialogue that builder this

builder needs a context in which I can't

ask my am context after that I can set

some options for this builder for

example I can set the text let's say

builder that set message this option and

in here we need to provide some message

for example let's say are you sure you

want to delete this book after that I

can also set some buttons for my other

Tyler for example I can say builder that

set positive button you can see that we

have negative button and positive button

for example for the positive button

that's a yes we also need an onclick

listener let's say new unclick the snap

this dialog interface that on click

listener and what would happen if the

user press on this yes and here is the

place that we need to remove the pot

from our ArrayList I can say if UTL

start get instance that remove from

already read let's also pass our book

groups that get with an index of

position if that was successful let's

show a toast message let's say Pope

after this toast message we also need to

notify that the data set has been

changed let's also set a negative button

for our dialog for example I can say

builder that set negative button let's

onclicklistener dialog interface that

inside this onclick method I am NOT

going to do anything because I want to

dismiss the dialog in case if the user

so we don't need to do anything we just

need to override this one click method

let's finish setting a negative button

after creating your builder after

setting the message the positive and

negative button you can create and show

your builder for example you can say

builder dot create dot show let's test

the application and let's see if

everything works fine let's go to our

all Box activity let's add a book to our

already read list and let's try removing

this book so if I press on this delete

you can see that we are seeing this

alert dialog are you sure you want to

delete 1q84 let's say no as you can see

even though we didn't write any code

inside this on click method we have

dismissed the dialog successfully let's

press the delete once again and let's

say yes this time as you can see the

book has been removed successfully that

alert Allah creates a much more better

user experience ok now that we have

rightt logic for already read books list

and let's quickly write for the others I

think I can copy and paste a lot of

these codes before copying and pasting

we need to go to our you to its class

and add some methods for example for

removing from different lists let's say

public boolean remove from one to read

let's also receive a book you can see

that the logic is exactly the same I'm

going to cut the process of writing the

logic for the other two lists you can

see that it's exactly the same ok now

let's go back to our adapter class and

let's copy the logic for T's already

read case I'm going to paste it for the

as you can see the code is exactly the

same we just changed the name of this

remove from favorites remove from

currently reading and remove from one to

read beside that I'm going to create an

onclicklistener for my different buttons

in main activity because I'm going to

navigate the user to each one of the

activities by clicking on the buttons

okay let's test our application let's go

to our all box activity let's add this

one to a currently reading list we are

navigating to the currently reading list

let's try removing this let's say delete

once again you can see that we are

seeing the dialogue let's say no this

time let's say yes it seems like the

book has been removed successfully if we

go back and if we check out currently

reading books you can see that the list

is a still empty let's quickly try for

others one to read added successfully

delete sorry I clicked on the current

view and not on the delete button let's

go back and let's try deleting it yes it

has been deleted successfully see all

books let's add it to our favorites

let's try to looking it let's say yes it

seems like we have an error when we try

to delete a book from our favorite lists

if we open our locket you can see that

something wrong is happening inside our

UTS class at 9 116 and yes this is the

error in here instead of removing the

I have recalled this method sorry about

that let's say favorites don't remove

let's try it once again let's add a book

to our favorites list and let's try

removing it let's say yes it seems like

it has been deleted successfully okay I

think that's enough for this video in

the next video we are going to see how

we can show a website in Android

applications ok see you in the next

in this video we are going to work on

this about button by clicking on this

button we are going to show some

dialogue in which inside that dialogue

we are going to show some detail about

the developer of this application and

also the application itself beside that

we are going to give the offer to check

our website by clicking on a button the

user will be navigated to our website

let's quickly see how we can implement

that for showing the dialog like the

previous video we can use the alert

dialog we are going to use that in here

but I also need to say that you have

other options as well for example you

can create your own customized dialog we

will talk about customized dialogue

later on in the course when we talk

about fragments but in here we are just

going to show a simple alert dialog okay

let's go to main activity and let's

implement that functionality that I was

just talking about so down in here

inside on create method I can say

let's say neon click listener we need to

create our alert dialog that builder

object in here once again I'm using the

Android X artifacts so import the right

one let's say other dialog dot builder

let's name it builder is equal to neon a

dialog that builder you know that we

need to pass a context in here because

we are inside the main activity inside

this interface we can pass main activity

after that we can set a title for our

other dialogue builder we can say

builder dot set title I believe is the

name of the method let's pass the name

of our application I can say get the

strings let's say our dot string dot add

name after that I can say builder touch

set message and let's provide a message

that's going to be our text and after

that we are going to set two buttons for

our dialog so let's say builder that's

at negative button for the negative

button I am going to say dismiss and

after that we need an onclick listener

so I have a toy point here let's say

dialog interface that include listener

once again inside this onclick method we

are not going to do anything because we

are going to dismiss the dialog we just

implement this onclick method after that

let's set a positive button for our

dialog let's say builder that said

positive button let's say visit neon

click listener and by clicking on this

visit text we are going to navigate the

user to our website for now let's just

add it to do in here we will do that

later on after creating the dialog we

can show it we can say Bueller that

creates that job also before I run my

application I am going to say that you

have all sorts of functionalities with

this builder for example if you take a

look at the available methods you can

see that you have all sorts of options

for example you can set an icon for your

dialog beside that you can set that if

your dialogue is cancelable or not by

saying set cancelable let's say that

cancelable this one you can pass a

boolean if the dialogue is not

cancelable the user cannot dismiss the

dialog unless and he or she clicks on

one of our buttons I'm not going to talk

more about these functionalities in here

because when we talk about customized

dialogue later on in the course you can

functionalities ok let's run the

application and let's see if we can see

this toyline let's click on this about

button right now I can only see this

visit button and that's because I've

made a mistake in here both of my

unclick listeners are for this set

negative button I need to change this

one to set positive button sorry about

that let's run the application one more

time once again let's click on this

about button this time you can see both

of the options also if you don't get my

point about being cancelable cancelable

means that if you click on anywhere

outside of the dialog for example in

here your dialogue will be cancelled if

you set your dialogue to not to be

cancelable you cannot cancel it by

clicking on anywhere on the screen you

just need to click on the dismiss button

ok let's also try this dismiss in here

we can dismiss our dialogue successfully

and by clicking on this visit button

because right now we don't have any code

once again our dialogue should be

ok let's write the code to navigate the

user to our website in order to navigate

the user to my website I'm going to

create another activity in my package in

Java folder in my package let's say new

activity empty activity let's name this

activity website activity in the layout

file of this activity I am going to put

only one element and that element is

going to be a webview let's search for

webview in here you can see that we have

this webview option let's drag that and

let's change its bits and height to a

match parent let's also give it an ID

I'm going to simply call it webview

that's all we need in here let's switch

back to our Java file and in here let's

initialize our webview I'm going to

define my web view as a member variable

as a private member variable inside this

activity and you will see why I am doing

this let's say private that view let's

name it web view down in here inside on

create method let's initialize that

let's say webview is equal to find V by

ID or that ID dot webview after that we

can pass a URL to this web view for

example if we want to show Google we can

save web view dot load load URL and we

can pass our URL let's pass the URL of

google.com and from the positive button

of our dialog let's navigate to this

website activity in here I can say

intent intent is equal to new intent for

the context let's fast main activity

that this for the destination website

activity dot class and we don't meet any

flag in here let's just say start

activity and let's pass our intent let's

run the application and that's if we can

load Google successfully let's click on

this visit as you can see we are

navigating to another activity but we

are not seeing google.com and that's

because in the URL we need to say HTTPS

because Google has SSL certification so

let's quickly modify our URL in our

website activity instead of HTTP I'm

going to say HTTPS let's run the

let's click on this about let's try

as you can see another application has

been opened in this case we are opening

Chrome because Chrome is the default

browser in this emulator this is good

but you can do better you can open the

website in your own application and

don't send the user to another browser

in order to do that you need to set a

webview client on your webview let's

quickly see how we can do that so in

here I can save fu that's that webview

client this one and we need to pass a

new webview client near webview client

this time if we run our application we

should open the google.com in our

application and not in another browser

about visit you can see that this time

we are inside our own application you

can see the name of application above in

here let's try searching something in

here for example let's try searching for

Android if we try to go back one page

right now if you press on this back

button we are going to go back to the

main activity this is not a good user

experience you may want to navigate the

user one page back and not destroy the

whole activity if you want to do that

you can overwrite the on back rest

method in here by pressing ctrl or and

searching for on back press we have seen

this method in previous videos

let's overwrite that and we need to do

some modifications in here and here is

the reason why I've defined this webview

as a member variable because I want to

have access to this method inside both

on back press method and also on create

method so what I can do in here is that

I can say if webview dot can go back

this method you can see that the return

type is a boolean if our web you can go

back let's say webview dot go back but

in the else case we are going to do the

super statement so I'm going to cut this

one and I'm going to put it inside this

else case this in here means that

whenever we are pressing the back button

if our web you can go back one page then

go back but if not do whatever you are

doing with your back button for example

destroyed activity and go to your main

activity let's try this let's visit

and let's search for something for

example may code this time if we go back

you can see that we are going back one

page and we are not destroying the whole

activity there is also one more thing

that you can enable on your webview you

can enable JavaScript if you want on

your webview as well most modern web

sites use javascript and you can enable

it in here if you want you can save web

view dot get settings this one dot set

JavaScript enabled this method you can

pass true or false in here for example

let's pass true but you can see that as

soon as I pass through I'm getting a

warning the warning says that enabling

JavaScript is a security issue and it

can cause vulnerabilities to your

application so enable it carefully okay

now that we have enabled JavaScript

let's try running our application one

more time and let's see if we can see

any difference we shouldn't see any

difference about visit you can see

Google in here and you can search for

whatever you want when you are using

webview in your application you have all

sorts of functionalities in fact a lot

of applications are based on web view

they are basically some website and they

are showing some webview in their

application so if you want to dig into

that area make sure to learn webview

well you'll have all sorts of options

when you are working with webview but in

this course we are going to use a web

view this much and we are not going to

go further in here I'm going to make my

website activity reusable because I may

want to show different websites in my

application for that I'm going to get an

intent in here and I'm going to receive

the URL with that intent so that I can

show multiple websites so before

instantiating it let's get the intent

let's say intent is equal to get intent

after that let's make sure that our

intent is not null so let's say if not

is not equal to our intent let's receive

the URL let's say a string URL is equal

to intent that get a string extra this

method and let's pass a key for example

let's say URL let's move this logic to

then I'm going to pass this URL to this

load URL method so instead of this

hard-coded text I'm going to pass URL

next in different part of my application

when I create an intent and navigate the

user to this website activity I am going

to also provide a URL for example in

here inside this onclick method of our

dialog before starting the activity I'm

going to say intent dot set extra or put

extra was the name of the method let's

say URL for the key and let's pass URL

let's remove this to do from here as a

suggestion in your application in your

blog activity you may want to provide a

link for more information about your

book let's quickly go to activity block

dot XML for example somewhere in this

layout you may provide a link for your

book for that you also need to change

the model of your book and provide a URL

for that and navigate the user to some

website if you want to give the user

some more functionalities but we are not

going to do that in here together

because that's really simple and I

believe you can do it by yourself ok I

think that's enough for this video it

was a relatively short video in the next

video we are going to see how we can

define some animations for example right

now when we navigate between different

activities we only have a basic pop-up

animation in the next video we are going

to see how we can create a better

animation for navigating between

different activities see you in the next

talk about animations in Android and

also beside that we will talk about how

to enable the UP button to be honest

with you we are not going to focus on

animations that much yet in the course

and after this video you will know my

reason okay let's see how we can

implement a simple animation in our

application for navigating between

different activities in order to create

a simple animation file in our project

inside app folder inside the resources

folder we can create any resources

directory by clicking on this new

Android resource directory from this

resource type we can select any the

first option in our list let's keep the

name anning and let's create our

resource directory now if you take a

look at your resources you can see this

einem folder by right-clicking on that

you can create a new animation resource

file I'm going to name this file a

slide-in let's create our file you can

see that the root element right now is

this set basically set means a set of

different animations for example you may

have a horizontal animation beside that

you may want to have a rotation

animation you can include them all

inside this set but in here we are only

going to implement one animation and

because of that I'm going to change this

root element I'm going to change it to

translate whenever you want to have a

simple horizontal or vertical animation

you can use this translate in this

application we are going to slide our

activity to the next activity

so in here we need a horizontal

animation let's see some of the

attributes on this translate element the

first one that I'm going to talk about

in here is called from X Delta this one

you can see that similar to that we have

this from void lttle you can guess the

meaning of each one of these when we use

the first one from X Delta it means that

we are going to define the horizontal

place of our animation where do we want

to start our animation in a horizontal

axis so let's say from X Delta in here

you need to define the first horizontal

place of your application for example

you can pass 0 pixel this is just a

normal pixel and it's going to be

started from the beginning of your

screen besides 0 you can pass 0% which

from the beginning of your element from

the beginning of the beats of your

so this percent in here means relative

if you pass percent P you are going to

start your animation from the zero pixel

relative to the parent of your element

not to the Viets of the element so for

example if we have a button that we are

going to apply this animation on that

this zero percent P in here means that

we are going to start our animation from

the beginning of its parent layout you

can enter any number that you want in

here from 0 to 100 beside that you can

also enter negative numbers for example

in here I am going to say negative 100

the next attribute that we are going to

take a look at in here is called 2x

Delta once again you can see that we

have two attributes 2x Delta and two Y

Delta you probably can guess their

meaning 2x Delta means the destination

in the x axis and two Y Delta is the

destination in the y axis mean here we

are just going to slide our activity so

we are going to use this 2x Delta you

can put whatever number that you want in

here but I'm going to say 0% P beside

these two you can also define a duration

for your animation as well for example

in here we can say duration you can see

that it's not working you can type it

manually you can say Android column

duration that's is equal to and we need

to pass our duration in milliseconds

inside these double quotations for

example I want to set the duration of my

animation to 1000 milliseconds so to

have a quick review in here our

animation is going to start from the

negative 100 pixel relative to the

parent layout and we are going to end in

the zero percent relative to the parent

inside the x-axis and the whole

animation is going to take one second

let's quickly create another animation

as well once again by right-clicking on

our animation folder that's a new

animation resource file let's name this

I think we can change the root element

from here and smell let's change this

one to translate and let's create our

XML file for this translate element I'm

going to define the same attributes but

I'm going to change their values for

example I'm going to say from X Delta

this time I'm going to pass 0% P let's

say 2x Delta this time let's pass

negative 100% DP or 100% peace sorry

about that and let's also define the

duration and rate column duration once

again let's say 1000 milliseconds okay

now we have two different XML files for

our animations how do we implement them

in our activities here is how you can do

that for example let's go to our all

books activity inside the oncreate

method of this activity before

everything we can say overwrite pending

transition you can see that this is an

inner method inside every activity this

method requires two animation files the

first one is the inter animation and the

second one is the exit animation let's

provide them for the first one I'm going

to say our thoughts annum dot let's say

slide in for the second one I'm going to

say our that einem dot slide out let's

run our application and let's see what

our animation looks like if we try to go

to all box activity you should see the

animation it's not that pretty but it is

what we created but in here if I try to

go back for example by pressing this

back button you can see that we are

still seeing the default animation if we

want to apply our own animation we can

do something like this in our activity

we can override a method by pressing

ctrl + o or alternatively by typing the

name of the method we can override that

method the name of this method is

finished so this method is going to be

called whenever we are going to finish

our activity let's call that after the

super statement once again we can use

this override pending transition let's

say overwrite pending transition this

time I am going to switch these two

animations for example for the first one

I'm going to pass a slide out and for

the second one I'm going to pass it

slightly so let's say our thoughts and

you dot slide out and for the second one

and if that slightly let's run the

application once again and let's go to

our old books activity this time if we

try this back button you can see that we

have some sort of animation it's not

perfect but it is what we have created

honestly I'm not a designer I am not

good at animating my applications but

probably you can do better than me just

play around with these numbers inside

your XML files and you will find

animations that you are looking for but

right now if we try to go to another

activity for example this already Redbox

activity you can see that we are still

seeing the default animation if you want

to apply your animation on this activity

as well once again inside this activity

you can overwrite the pending transition

or alternatively if you want to apply

the animation on your entire application

you can change the style let's quickly

see how we can change our style so

inside our values folder inside

styles.xml in here I am going to create

another animation sorry I'm going to

create another style let's say it style

I'm going to name my style custom

animation and for its parent I'm going

to say at Android column style forward

slash animation dot activity so this is

going to be our parent inside this style

file I'm going to define some items for

example for the first one I'm going to

name it activity open inter animation

this one and for its value I'm going to

pass my own animation I'm going to pass

this slightly I can say that any slide

in I need to create three more items the

next one is going to be activity open

exit animation this one this time for

its value I'm going to say add and slide

out let's also create the exit

animations item activity close inter

animation this one let's pass a slide

out once again at Panama slide out

another item activity close exit

animation this time let's pass our slide

in now that I have created this style I

can pass it as an item inside this app

theme style so in here inside this F

theme style I can say item for its name

I'm going to say Android column window

animation style this one and for its

value I'm going to address this file I'm

going to say add style forward slash

constant animation now that we have

changed our app theme style we can

delete that overwrite pending transition

method from inside our Albert's

activity so let's delete this one and

also beside that let's delete this whole

and finish method let's run our

application one more time and let's try

going to different activities for

example this currently reading books you

can see that we are seeing some sort of

animations let's go to this see your

favorites animation my emulator is low

on speed so for that you can see some

frames let's go to our all books once

again we can see the animation to our

book activity it seems like our

animation have been applied successfully

there are much more concepts and

elements when creating different

animations you can probably and design a

simple game with Android studio by just

using these animations but I'm not going

to talk about them in here the reason

that I'm not going to talk about them in

here is that because the Android team

are releasing a much better solution for

animations that solution is called

motion layout and right now it's in beta

we'll be released in a few monsters

probably in the spring of this year in

the Google i/o conference or later on

this year in Android developers

conference either way when it's released

on a stable Channel I will create one or

more videos about that I've seen and

I've heard a lot of good things about

that let me quickly show you some links

if you come to this web page at Android

developers official website you can see

some of the features of motion layout

together with the motion editor you have

all sorts of functionalities and all

sort of easiness when you are designing

your animations honestly I think that

they are drinking After Effects inside

Android studio so for that I'm not going

to talk about animations in here instead

I'm going to wait for the motion layout

motion layout is going to compete

constraint layout 2.0 and that

constraint layout is still in beta

phases we just need to wait a few more

months ok let's move on from animations

the next thing that I'm going to do

inside my application is that I'm going

to enable an UP button in my activities

for example inside this all works

activity but before I do that I'm going

to delete my animation because I don't

like it let's just comment this line and

let's close all of these extra points so

in order to activate your off button

inside on create method of your activity

you can say get action bar or to refer

circuit support action bar dot set

display home op enabled please option in

here if you pass through we will

activate your op button let's run the

application and let's see what does that

look like if we go to our all box

activity in here you can see this back

arrow which is our off button right now

it's not going to do anything because we

haven't defined the functionality but if

we want to navigate the user back to the

main activity we can do something like

this we can overwrite the on option item

selected method like this I'm talking

about this method you can see that we

are getting a menu item and we can use

that item in here we can create a switch

statement let's say switch on item dot

get item ID and let's create our cases

let's say in case it's Android that our

that ID at home which means that

you are going to click on our up button

this is the idea of that button we are

going to navigate the user back to the

main activity and here I have two

options I can create an intent and

navigate the user back to the main

activity or I can call the on backrest

method let's call that so this in here

means that do whatever you are doing

when the user clicks on the back button

basically the up button and the back

button in here are going to have the

same functionality but of course you can

do whatever you want you can navigate

the user to another activity let's also

add a break in here and let's create a

default case in the default case I am

NOT going to do anything I'm just going

to break out of the switch statement

let's run our application and that's if

it's going to work so if we go to our

all books activity if we click on this

up button you can see that we are

navigating back to the main activity I'm

not going to enable it in other

activities I just wanted to show you how

you can implement this out button okay

the next minor thing that I'm going to

do in here is that to change the name of

my application this title in here in

different activities for example I'm

going to change it inside these are

books activity to all books in order to

do that you can go to your manifest file

and in here for different activities you

can define different labels but I'm

going to create my labels inside the

string resources so inside my values

folder inside strings.xml I'm going to

define a few more strings the first one

is going to be named activity all books

and its value is going to be all books

after defining these strings you can go

back to your manifest file and inside

every activity tag you can set a label

attribute for example for this favorite

activity we can say label let's search

for favorite activity let's do the same

thing for the other activities let's run

our application and let's see if you

have changed the labels successfully in

the main activity we are still seeing

this my library which is the name of our

application let's go to our all books

activity you can see that the title has

been changed if we go to our book

activity you can see the pop details

let's go to already read activity once

again you can see the title has been

changed it seems like we have changed

the labels in all of our activities okay

I think that's enough for this video in

the next video we are going to work on

our utils class right now we are using a

static array lists for our data which is

not resisted over the life cycle of our

application in the next video we are

going to see my simple solution for

persisting data even if we restart our

device it is probably the last video of

this section of the course so make sure

to don't miss that ok see you in the

in this video we are going to solve our

problems with our data not being

persistent right now the problem is that

we are using static variables for our

data for example when they add one block

to one of these lists that book will be

added but when we close our application

these ArrayList will be cleared in this

video we are going to solve that we are

going to persist our data after an

application is closed and also for that

matter after the device is rebooted

usually in a real world application you

may want to use databases for situations

like this they have been designed

exactly for this problem and they have

been designed to persist our data but we

don't know anything about databases yet

later on in the course we will talk

about databases specifically we will

talk about SQLite database and also its

wrapper room database but we also have

another option that we are going to use

in here that option is called shared

preferences the purpose of shared

preferences is that to produce the data

that is not a structured they are being

void to use for the Preferences of the

user in your application for example if

the user decides to use the dark theme

you can save that preference in your

shared preferences but that's not all of

the purpose of the shared preferences as

I said you can save all of the on

structured data in shared preferences in

here in our application our data is a

structured we have a model called book

beside that we have all of these array

lists but we are going to manipulate our

data and we are going to save them

inside the shared preferences by

manipulate I mean we are going to

convert our Java classes and array lists

and after that we are going to save them

inside the shared references in another

word we are going to serialize our

objects and later on when we get our

data from the shared preferences we are

going to convert those strings to these

array lists and books that process is

called deserializing okay enough talking

shared preferences so if you remember

from the previous videos I have done all

of my interactions with Maya arraylists

inside this utils class and I've done

that because of this exact reason I'm

going to delete all of my array lists

and I am going to use shared references

so most of our changes are going to be

inside this utils class first of all I'm

going to define my shared preferences as

a member variable inside this utils

class for example down in here I'm going

to say private shared preferences you

can see that this is an interface that

comes from Android content package let's

name it shared preferences after that

I'm going to initialize it inside my

constructor inside these UTS before

everything let's say shared preferences

is equal to get shared preferences but

we cannot use this method because for

that we need a context for that reason

I'm going to receive a context via the

constructor of this class but notice

that and because I'm going to receive a

context in here I need to change a lot

of codes in my application wherever we

have used this constructor or for that

matter this instance and its method get

instance method we also need to pass a

context we will do that later on

so let's receive a context let's say

context and down in here let's say

shared preferences is equal to context

dot get shared preferences you can see

that in here we need a name this string

is going to be the key for our shared

preferences let's pass a name for

example let's say alternate divi divi S

stands for database after that after the

key you also need to pass a mod for

example the mode that I'm going to pass

in here is this mod private we have

other modes as well but if you want your

shared preferences to be specific to

your application only you can use this

mod private or to be precise context

that mod private now you have an

instance of your shared preferences you

can use it however you want you can put

some data into it or you can get

existing data from your shared

preferences but right now because I've

is an a constructor we should probably

see some error inside to get instance

method because if you remember in here

we are calling our constructor for that

inside this get instance method I'm

going to also receive a context and I'm

going to pass it to this constructor

that will fix our error for now next I'm

going to change this init data method in

here right now we are saving our books

inside these all books array list which

is a static array list but let's see how

we can use shared references so in here

first of all I'm going to define a new

array list let's say array list of books

let's call it books is equal to new

array list and after that I'm going to

add my books to this new ArrayList and

not to the static ArrayList so let's say

books that add and similarly for the

second book now let's see how we can add

these books I released into our shared

preferences so down in here I can say

editor this interface shared preferences

that editor let's name it editor is

equal to our shared preferences instance

dot edit you can see that this edit

method returns an editor instance after

that with the help of this editor we can

say editor dot for example put a stream

you can see that our options in here are

very limited we can only store primitive

datatypes plus the string but how do we

store our Java classes for example this

book class and similar to that our

ArrayList inside these shared

preferences I said that we are going to

convert our books I read list into a

string let's see how we can do that the

best option is to convert your Java

classes and array lists into a JSON file

if you don't know anything about JSON

don't worry we are going to talk about

that later on in the course specifically

we will talk about it in the networking

section basically JSON is a way of

passing data between different

godless of the language I mean here we

are not going to talk further about JSON

we are not going to work with JSON files

we are going to handle the job to a

third-party library so basically we are

going to serialize and deserialize our

objects with the help of another library

let's quickly implement that library

into our project the name of this

library is JSON if you search for JSON

you can see that the first thing from

github is the link of this library as

you can see above in here it has been

developed by Google down in here

somewhere we should see the dependencies

we are using Gradle not maven so we can

copy the dependencies from here let's

add it into our project inside build

that Gradle module app let's add it

somewhere and let's sink our project

after adding it in our routines class

first of all let's create an instance of

this JSON object we can say Giza you can

see that it's coming from countered who

built it Doosan package let's name it

JSON is equal to new JSON after that if

you want to convert an object to JSON

and you can say something like this you

can say geez on dot to JSON we have

multiple versions of this to JSON method

you can see that each one of these

versions receive different arguments for

example we can simply pass our books so

this way we can have a string let's

simply name it text is equal to json dot

to json so this way we can serialize our

books object with the help of this

reason we have converted our ArrayList

into a JSON file now let's see how we

can add this text into our shared

preferences I'm going to delete this one

I'm going to say editor that put the

string first of all we need the key I'm

going to use constants for different

keys and I'm going to define them above

in here as member variables let's say

private static find out the string

let's name it all box key let's

initialize it to all books after that

down in here inside this put a string

method we can pass that key let's say

all works key and after that we need our

value which I'm going to say jisan but

to JSON and let's pass our box object as

simple as that with the help of this

editor we can put this ArrayList into

our shared preferences but there is one

more step and we need to apply the

changes on this bed être for that we

have two options we can say editor dot

apply this method or the alternative

that we are going to use in here is dot

commit the difference between the apply

and commit is shown in here inside this

file and so whenever you use apply the

changes inside your shared preferences

will be applied in a background thread

and you will not block the main thread I

suggest that in most cases you use apply

because you don't want to block the user

from interacting with your application

but in here our data is really small and

we are not going to block our user

interface for long and beside that we

need the result of this applying

immediately for that I'm going to use

this comment later on we will see that

how we can use callbacks in order to

communicate between two different

threads and then we can use apply but in

here because we need the results

instantly and we haven't talked about

callbacks I'm just going to simply use

this comet method okay that's all that

we need to know in order to put some a

string into our shared preferences now

that we have successfully initialized

our data let's see how we can call this

in its data method so inside the

constructor if you remember in here we

are calling this in its data but before

that we are using these all books are

released in order to make sure that we

haven't defined outputs previously as I

said I'm going to delete all of these

array list so I shouldn't use these all

box ArrayList for that I'm going to

check my shared preferences and see if I

in the shared preferences or not if I

don't have any initial data I'm going to

call this in its data method but if I

don't I'm going to escape to the rest of

the code okay let's see how we can get

our data from our shared preferences the

right place to do that is inside the get

all box method let's quick answer for

that you can see that we have this

method in here and we are simply

returning all books ArrayList instead of

that I'm going to get the data from the

shared preferences let's say I really

stopped different book let's name it

books is equal to in here first of all

I'm going to get the text from the

shared preferences and after that with

the help of JSON library I'm going to

convert it to this books ArrayList so

before defining this ArrayList first of

all I need to create an instance of the

JSON so let's say juice on jihad is

equal to new JSON after that let's say I

really stuff different books is equal to

json dot from json this time we can see

that similar to to json we have these

from json as well in here first of all

we need the text itself which we are

going to get from shared preferences but

as you can see I'm not getting my shared

preferences and that's because when I've

defined my shared preferences I didn't

define it as a static variable and

because of that because we are trying to

have access to a non-static field if I'm

inside a static method we are getting

this morning let me type it completely

to see the error if you hover over these

shared references you can see that

non-static field cannot be referenced

from a static context for that I'm going

to delete this static keyboard from the

Declaration of this method we have used

it so far in order to have access to

this all books ArrayList but we no

longer need it so we can safely delete

it now that we have access to our shared

preferences I can say shared preferences

insightly's get a string method first of

all we need a key the key is going to be

our constant all books key this one and

after that we need a default value which

I am going to say not in this case so if

we did not get anything from the shared

preferences we are going to return null

as this string after that the next item

that we need an effort is from JSON

method is a type token the type token in

here defines that to what object we are

going to convert our JSON in this case

we are going to convert our JSON to an

array list of books so we need to create

a appropriate type so in here I can say

type you can see that it's an interface

let's name it type is equal to new type

token this one has the data type of this

type token inside the diamonds I'm going

to say array list of different books

after that we have a strange syntax in

here after the parentheses I'm going to

put a pair of curly braces after that a

dot and after that this gets type method

which you can see that will return a

type so let's use that this is fairly a

strange syntax and we haven't seen it so

you don't need to understand everything

in here we are just defining a new type

token you can copy and paste this one if

you need basically inside these type

token diamonds we are defining our

object kind and after that we are using

this dot get type method in order to

have a type after creating our type in

here inside this from json method we can

pass that now we are getting our books

from the shared preferences and we are

converting it to an ArrayList after that

we can safely return books instead of

all works so now that we have changed

this get out box method we can call it

from inside our constructor inside these

utils instead of using these all books

I'm going to say if null is equal to get

all books this method if you remember we

had a lot of non potentials inside to

get all box method let me quickly show

you one more time so for example if we

fail to retrieve this string from our

shared preferences we are going to get

known after that if our type doesn't

work we are going to get now which will

be produced by this JSON library so

there are a lot of potentially null

values so make sure to take care of them

whenever you call your methods so inside

this constructor I'm going to say if

null is equal to get all books I'm going

to call this in its data method let's

remove this line of code because it's no

longer necessary and if you want to have

a review inside this in its data method

we are initializing our data we are

creating these books ArrayList and we

are saving it inside the shared

preferences so the logic that we have

wrote so far means that if it's the

first time that the user is launching

our application if we don't have any

books saved inside our shared

preferences then call this in its title

method and save some ports but if it's

not the first time that the user is

launching our application just ignore

this if statement after initializing the

initialize these other array lists as

well because even if at the time of

installing our application these array

lists should be empty but we are using

them inside different activities and

based on them we are calling some

methods if these array lists are none we

are going to cause some exceptions for

that I am going to initialize all of

these with some empty array lists you

can see that basically inside these if

statements we are doing the same thing

for our aesthetic array lists this time

we are going to do it for our shared

preferences so I'm going to do the same

thing that I have done for my initial

data instead of these already read books

I'm going to use get already read books

if you remember we had such a method

down in here let's quickly find that we

have this get already read books

method and we are simply returning our

ArrayList this time let's see if we have

such a data in our shared references

once again I'm going to say jisan let's

say Tucson is equal to new JSON after

that let's define our type once again we

are using this interface which is coming

from the java packages so let's say type

once again let's name it type is equal

to I think I can copy some of the code

from inside this get out box method

let's copy everything we just need to

also we need to remove this a static

keyboard because we no longer need that

of course removing this static keyboard

is going to cause some problem in our

application for example inside already

read book activity in here without

initializing our utils we are trying to

call this method which was fine when we

have defined our method a static but

it's not going to work right now we will

fix this later on ok let's move on from

this part and let's go to our UTS class

inside this kit already read box method

when we are trying to get a string from

the shared preferences we need to put

another key in here let's quickly define

after defining these constants we can

pass them in different methods for

example for this gate already read books

method I can pass already read books and

constant now that we have changed this

gate already read books method inside

our constructor inside these utils when

we are going to initialize our already

read books we need to check that if it's

non or not let's say get already read

books to his method if it is not we are

going to initialize our shared

references because I am going to use my

editor in multiple places I'm going to

define that outside of these if

statements for example in here let's say

editor to be precise shared references

that editor let's name it editor is

equal to shared references that edit

then after that inside this if case we

are going to edit our shared references

I can say editor that put a string for

the key I am going to use my key from

above in here this one let's say I

already read books and for the values I

am going to pass an empty array list I'm

also going to use JSON libraries so

let's define our JSON above in here

let's say jisang is equal to a near json

after that inside this put a string

method let's say json dot to json and as

for the object I am going to say new

this way we are initializing our already

read books as an empty array list inside

our shared preferences we just need to

commit these changes we can say anything

commit let's do the same thing for the

other array lists as well for example

for this one to read books we need to

fix the get one to read books method if

you remember we had such a method down

in here let's copy everything from

inside this get already read box method

I'm going to copy everything and in here

let's paste them we just need to delete

this get a static keyboard and also

beside that use another key then after

that inside the constructor we need to

check that if this method is going to

return non or not let's say if not is

equal to get one to read books then we

are going to initialize our one to read

books ArrayList let's copy these two

line of code from here and let's paste

them in the second if case we just need

to change this constant similarly for

the currently reading book and favorite

books let's copy the logic from here and

paste them inside this gate currently

reading book method let's also delete

this a static keyboard and let's change

the constant let's do the same thing for

this gate favorite books method

delete the static keyboard and change

the constant let's minimize both of

these methods and let's go back to our

constructor let's say if null is equal

to get quietly reading books this one

let's copy these two line of code and

let's change the constant beside that in

here let's say if null is equal to get

favorite books once again let's paste

these two line of codes and also let's

okay now we have deal with our

constructor successful if we have

initialized all of our array lists let's

see what else do we have inside this

utils class we have fixed all of these

methods until down in here after this

get favorite books we also have this get

books by ID method let's quickly see

what will be having here so basically

once again we are using the all books

are released in order to get some pop by

its ID instead of that I'm going to get

the books from my shared preferences for

that I'm going to say array list of

books let's name it books is equal to

get all pubs I'm going to use my method

after that I'm going to check that if

these books are a list is null or not

let's say if null is not equal to books

then let's put our for loop inside that

if case and also let's iterate through

our books ArrayList that's all the

change we need to do inside this get put

by ID method now we are getting the book

from our shared preferences instead of

ArrayList after that we have these I had

two methods and is remove from method

let's quickly fix this as well inside

this method we are returning the result

of this dot add method which we have

called on our ArrayList this time I'm

going to connect my shared preferences

so I'm going to say negative stuff

different book let's name it books is

equal to let's say get already read

books if you remember above in here we

have fixed that method I'm talking about

this method in here and now instead of

using our ArrayList we are getting the

data from the shared references then

inside these two already read method we

are going to use that after that we need

to make sure that these books are a list

is not known let's say if not is not

equal to books after that let's say if

our books ArrayList that at

let's say book if the result of that is

then we are going to save these boats

are released into our shared preferences

as a reminder this add method will add

the book into our ArrayList and after

that we'll return through if something

wrong happens it will return false so

after this check in here inside this if

statement we have successfully added the

book into our list now we need to

convert this books ArrayList into a JSON

file and after that added to our shared

references for that I'm going to

instantiate address on in here and say

ji-sun is equal to new JSON after that

I'm going to instantiate my editor let's

name it editor is equal to shared

references that edit and after that I am

going to first of all remove the current

already read books and immediately after

that I'm going to put this new books

ArrayList so let's say editor dot remove

you can see that beside put a string and

get a string we have this remove as well

if you want to clear your shared

references you can use this clear method

which will remove all of the data inside

your shared references with the key that

you have provided above in here when you

have created your shared references I'm

talking about this key in here this

alternate TV it will clear all of the

data inside that shared preferences but

in here we are not going to clear all of

the data we are just going to clear our

already read books list and we are going

to update it with this new list so let's

use that remove method which requires a

key once again for the key I can pass my

constant already read books after that

let's say any third that put a string

for the key once again let's say already

read books and for the value let's say

Jason taught to JSON and let's pass our

books are released after everything we

just need to call that commit method if

we reach to this point we also need to

return true because as you can see the

return type of this method is abloom Ian

if we reach to this point it means that

we have successfully updated our share

preferences so we can safely return true

but in case if anything wrong happens in

this process we are going to return

false I'm going to do that after

everything let's say return false that's

all we need to do in order to add a new

book to our already read book list in

our shared preferences let's copy this

logic for the other methods for example

for this ad to want to read list let's

delete this return statement in here and

let's paste our logic we just need to

change this method let's say get one to

read books and after that we need to

change these constants as well once

again we want to read books ok let's do

the same thing for the other methods for

this currently reading let's change the

name of our method to get currently

reading books and after that let's

change our constant let's say currently

reading books let's minimize this method

and let's do the same thing for our last

method for this add to favorite method

let's say get favorite books and for the

constant let's say favorite books

okay I think that's enough for this

video this video is getting a little bit

long but we also have these remove

methods in which we are going to fix

beside that we have a lot of problems in

different part of our application

because first of all we have changed the

constructor of this you Tunes class and

also we have removed a static keyboard

from the Declaration of some of these

methods we will fix those problems in

the next video as well okay see you in

in the previous video we have rewrite at

this UTSA class up until these removed

methods in this video we are going to

change these remove methods in order to

get our data from the shared preferences

not static array lists beside that I

said that right now we have a lot of

problems in our application due to

changes in this utils class you can see

some red warnings above in here we are

going to fix them in this video as well

okay let's change this remove from

first of all let's delete this return

statement after that let's get already

read book let's say array list of

oops is the call to get already read

books after that I'm going to check that

if this array list is null or not let's

say if books or if not is not equal to

books if that's the case we are going to

remove the book from this list in here

you may think that you may write some

logic similar to these add methods for

example inside this add method after

checking that if our array is null or

not we are using this add method in

order to add our new book in here you

may want to do the same thing for

example you may want to say if books

taught remove the book that we are

receiving you may think that this is

I have tried that actually and the

reason for that is because this book

that you are passing to this method is

different from the book that is inside

your ArrayList the values are the same

for example the name IT description and

everything is the same for both of these

books but the reference is not for that

you cannot remove your book this way

instead I'm going to create a for each

loop let's say for pork let's name it be

inside our box ArrayList after that

inside the for loop let's say if B dot

ket PI D is equal to this incoming box

ID book target ID if that's the case

then we are going to remove this pot so

this way we are not checking the

reference of these two objects instead

we are checking their equality by their

ID so if that's the case we are going to

don't remove let's say be it's very

important to pass be in here and not

this incoming book or if you want to

have the boolean you can say if books

that remove let's pass P once again if

that's the case we are going to update

our shared preferences let's do that in

first of all we need an instance of our

JSON let's say is equal to new JSON

after that I can say editor let's name

it editor is equal to shared references

after that I can say editor dot removed

first of all we are going to remove this

already read book from our shared

preferences for that I need the key

that's math already read books after

that I'm going to put the new books

ArrayList let's say editor that put a

string or the key I'm going to say

already read books and for the value I'm

going to say json dot to json our books

are released after that lets say editor

dot commit in order to commit our

changes also the return type of this

method is a boolean so we need to pass

through in here after this editor that

commit if we reach to this point in our

code it means that we have successfully

removed a book from our shared

preferences so we can safely return true

but if anything wrong happens during

this process we need to return false

i'm going to do that after everything we

need to do the same thing for the other

three remove methods so let's copy all

of these and let's paste them inside

this remove from one to read we just

need to change the name of our method in

here to get one to read books and also

okay I think that's all the changes that

we need to do inside this utils class

that's where you can check everything we

have changed these remove methods we

have changed these add methods we also

have changed this get proper ID method

we change the gather methods for our

lists we also change this init data

method and after that we have changed

this constructor we no longer use these

array lists so I'm going to comment them

okay now let's fix our problems in our

application I'm going to check my

classes one by one so in the project

folder inside the package folder let's

check our classes one by one all books

activity first of all we have this error

in here we are using this get instance

if you remember this get instance now

requires a context which I'm going to

pass this you can see that we don't have

any much error inside this class let's

go to the next one I already read both

activity because we have removed a

static keyword from the Declaration of

this get already read books method I'm

going to fix that by calling to get

instance method let's say you tips that

get instance in which requires a context

in which I can pass this okay that's all

the fix that we need to do inside this

already read book activity let's go to

our book class because this is the model

and we haven't used anything from inside

the UTS class we don't need to change

this one inside the book activity we

have multiple errors you can click on

these errors from this left pane in here

in order to navigate to the errors for

example in here we need to pass a

context let's pass this let's check the

second one once again in here we need to

pass context the third error in here we

need to pass a context but because we

are inside this onclick listener we need

to pass group activity dot this instead

of this let's see others inside this

handle currently reading once again

that's passed this inside I click

listener of this between our two

currently reading I need to say book

in here we need to pass this also inside

this onclick listener of this BT an ad

to want to read let's say both activity

dot this that's probably all of the

changes that we need to do in our

application we just need to pass some

context to our get instance method let's

save this and let's check the last one

so let's say work activity that this I

think we have fixed all of the errors

inside this class let's check the others

inside the recyclerview adapter from the

onclicklistener of our positive button

of our alder toilet if you remember

inside this adapter we have received a

context where the constructor so I can

see damn context let's check others once

again let's pass in context in here as

well in context the last one that's here

let's say am context ok it seems like we

have fixed everything inside this

adapter let's switch to a currently

reading activity once again in here

because we have removed a static

keyboard first all we need to say get

instance and we need to pass our context

favorite activity let's say YouTube

start get instance and let's pass this

inside the main activity I believe we

have instantiated our routines let's

pass our context we have fixed the UTS

class we shouldn't see any error in here

let's go to one to read activity once

again we need to say gluten start get

instance and we need to pass this I

believe that was the last error in our

application let's also check the website

activity we don't need to change

anything inside this class ok now that

we have rewrite the logic for our

application let's test it and let's see

if everything works fine our application

is launching that's a good sign

let's go to our all books activity in

here we can see our books once again

that's a good sign let's see if we can

see the details of this book by clicking

on this button we are seeing them let's

also go to our book activity in here we

are seeing all of the details of our

book let's try adding this book to one

of our lists for example this one to

read it seems like we have added the

book successfully let's see if we can

see the details in here we can see them

we can see this delete water but here

comes the difference between using

aesthetic variables versus shared

preferences right now if we close our

application and run it once again we

should see this book still in our wish

let's close the application and let's

run it once again and let's see if we

can see this book in our wish list let's

run it once again let's go to our wish

list and as you can see we have our book

in our wish list now we have persisted

our data with the help of shared

preferences it seems to be great let's

also try to leting this book from our

I believe in here we should see a little

bug let's try deleting this book first

of all let's say no next time let's say

yes it seems like the book has been

removed successfully but we are seeing

the book inside our wish list I believe

the problem is that our recyclerview is

not refreshing if we go back to the main

activity and we open our wish list once

again you can see that the list is empty

but for some reason after deleting the

book the recyclerview does not refresh I

believe the reason for that is because

the process of deleting that book from

our recycler view takes too much time

and we have a trading issue in here if

you take a look at our recycler view

adapter this phonebooks recycler view

adapter you can see that after removing

the book from our lists immediately

after that we are calling these notify

data set changed we have seen the toast

message we have seen this book remove

text but it seems like this method in

here is not being called until this

point until calling this method we have

removed the book successfully from our

list but the process of updating the

process of making another connection to

the shared references inside for example

and I get favorites method takes too

much time and before that we have called

this method so we have called this

method before we get the new favorite

ports we can fix this we can create a

callback interface and create a

communication between this part of our

application between this on-click method

and for example favorite books activity

we can implement that callback interface

favorite books activities so that

whenever we remove some book inside this

on click method we update list of our

books but I'm not going to do that in

here because we haven't talked about

call back interfaces yet if you want as

a challenge for later videos you can

come back to this video and fix this

problem when we have talked about call

back interfaces I believe we will face

this problem a lot during the course and

we definitely will take a look at call

back interfaces and their usages in

situations like this so for that reason

I'm not going to talk about the solution

for that issue in this video let's

quickly check the other aspects of our

application for example let's add some

books to other lists let's try this book

let's say already read we have added the

book let's delete it let's say yes what

has been removed if we go back to main

activity and check our already read

books activity you can see that the list

is empty okay I think that's enough for

this video and for that matter for this

section of the course you have

successfully created your first

functional application as a reminder of

what we have done in this section I'm

going to say that we have practiced a

lot of our skill set beside that we have

learned how to show different dialogues

we have seen how to create a web view

and show our website beside that we have

seen how to create expandable record

views we have seen how to use aesthetic

beside that we have learned how to use

shared preferences we learned how to

enable this off button we learned how to

create animations for our activities we

also have learned how to change the

title of different activities I believe

overall this was a good section and I

hello everyone may Symes here this video

is about to reached its end but before

that I would like to say that it is

amazing that you have watched thus far

of the course make sure to have a little

party watching the entire course means

that you are serious about Android app

development because of that once again

I'm going to remind you that there is an

extended version of this course that you

can take there are more than 60 hours of

videos in that course and you will learn

everything that you need for a

successful career in Android app develop

by enrolling in the course you will have

lifetime access to all of the existing

videos and all of the new videos that

I'll add in the course you will have

access to the source code that I write

in the videos and you can ask your

questions directly from me and expect an

answer between hours above all you will

have 30 day money-back guarantee in case

if for any reason you changed your mind

click on the link in the description of

this video or go to Mako dot org for

more information about the course

remember that you can use free code camp

as the coupon code to get 20% discount I

hope you learned something in this

course take care and continue coding