All language subtitles for 004 Quick Breather and Review_en

In the last section, we finished up a refactor that moved a bunch of logic from our main function inside

of the main dart file into a new custom widget that we defined inside of our app dart file.

Inside the outdoor dirt file, we created a new custom widget by defining a new class that extended

the base class of stateless widget.

We made this a stateless widget because we did not expect it to have to maintain any of its own data.

That would change over time.

That might change at some point, and it might change very shortly.

But at least for right now, it was a good place to get started.

Any time that we define a custom widget, we must define a method on that custom widget called Build

the build method has three requirements.

First off must be called built.

That's obvious enough.

Secondly, it must return a widget.

Third, it must accept a single argument that we referred to as context.

And you'll sometimes hear this referred to as the build context because that's technically the type

of the value that gets passed in.

We will eventually come back and talk a lot more about what this context thing is.

But for right now, we're just going to gloss over it a little bit.

So then inside of our build method, we assembled a new material app widget that had all of its own

custom widgets nested inside of it.

We then return the entire thing.

Then back over inside of our main dirt file, we imported the custom map widget that we just created.

We then created a new instance of that widget and passed the instance off to the run app function.

Then presumably behind the scenes run app took that instance of our app widget, and I assume at some

point time probably called this build method right here.

It got back all these definitions of what our app is supposed to look like and then rendered all those

widgets onto the screen of our mobile device, so that's a review of where we're at right now.

Now, before we move on, there's one last little concept I want to reveal here.

OK, so this is what we refer to as our widget tree, and it's a very handy way of visualizing all the

different images that are being displayed inside of our application.

So at this point, everything inside of our application is being rendered ultimately by the app widget

that we just put together.

The App Widget is returning from its build method, the material app widget.

So as a direct child to the app, we have our material app.

Then as a direct child to the material app, we have the scaffold that we put together.

Then the scaffold itself shows two widgets, the floating action button and the app bar, and each of

those are showing its own respective widgets of icon and text.

So again, this is a handy way to picture our widgets as they are built inside of our application.

And we're going to eventually create a couple of different diagrams like this to better understand the

flow of data inside of our application when we start introducing state or data that changes over time

inside of our app as well.

OK, so that's a good review.

Let's take a quick pause right here.

We're going to come back the next election and we're going to start working on the next piece of functionality

inside of our app.