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that follow Material Design. A Material app starts with the |
MaterialApp widget, which builds a number of useful widgets |
at the root of your app, including a Navigator, |
which manages a stack of widgets identified by strings, |
also known as “routes”. The Navigator lets you transition smoothly |
between screens of your application. Using the MaterialApp |
widget is entirely optional but a good practice. |
<code_start>import 'package:flutter/material.dart'; |
void main() { |
runApp( |
const MaterialApp( |
title: 'Flutter Tutorial', |
home: TutorialHome(), |
), |
); |
} |
class TutorialHome extends StatelessWidget { |
const TutorialHome({super.key}); |
@override |
Widget build(BuildContext context) { |
// Scaffold is a layout for |
// the major Material Components. |
return Scaffold( |
appBar: AppBar( |
leading: const IconButton( |
icon: Icon(Icons.menu), |
tooltip: 'Navigation menu', |
onPressed: null, |
), |
title: const Text('Example title'), |
actions: const [ |
IconButton( |
icon: Icon(Icons.search), |
tooltip: 'Search', |
onPressed: null, |
), |
], |
), |
// body is the majority of the screen. |
body: const Center( |
child: Text('Hello, world!'), |
), |
floatingActionButton: const FloatingActionButton( |
tooltip: 'Add', // used by assistive technologies |
onPressed: null, |
child: Icon(Icons.add), |
), |
); |
} |
}<code_end> |
Now that the code has switched from MyAppBar and MyScaffold to the |
AppBar and Scaffold widgets, and from material.dart, |
the app is starting to look a bit more Material. |
For example, the app bar has a shadow and the title text inherits the |
correct styling automatically. A floating action button is also added.Notice that widgets are passed as arguments to other widgets. |
The Scaffold widget takes a number of different widgets as |
named arguments, each of which are placed in the Scaffold |
layout in the appropriate place. Similarly, the |
AppBar widget lets you pass in widgets for the |
leading widget, and the actions of the title widget. |
This pattern recurs throughout the framework and is something you |
might consider when designing your own widgets.For more information, check out Material Components widgets.info Note |
Material is one of the 2 bundled designs included with Flutter. |
To create an iOS-centric design, |
check out the Cupertino components package, |
which has its own versions of |
CupertinoApp, and CupertinoNavigationBar.<topic_end> |
<topic_start> |
Handling gestures |
Most applications include some form of user interaction with the system. |
The first step in building an interactive application is to detect |
input gestures. See how that works by creating a simple button: |
<code_start>import 'package:flutter/material.dart'; |
class MyButton extends StatelessWidget { |
const MyButton({super.key}); |
@override |
Widget build(BuildContext context) { |
return GestureDetector( |
onTap: () { |
print('MyButton was tapped!'); |
}, |
child: Container( |
height: 50, |
padding: const EdgeInsets.all(8), |
margin: const EdgeInsets.symmetric(horizontal: 8), |
decoration: BoxDecoration( |
borderRadius: BorderRadius.circular(5), |
color: Colors.lightGreen[500], |
), |
child: const Center( |
child: Text('Engage'), |
), |
), |
); |
} |
} |
void main() { |
runApp( |
const MaterialApp( |
home: Scaffold( |
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