| // Copyright 2014 The Flutter Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| import 'package:flutter/material.dart'; |
| |
| void main() => runApp(const MyApp()); |
| |
| class MyApp extends StatelessWidget { |
| const MyApp({super.key}); |
| |
| // This widget is the root of your application. |
| @override |
| Widget build(BuildContext context) { |
| return MaterialApp( |
| title: 'Flutter Demo', |
| theme: ThemeData( |
| // This is the theme of your application. |
| // |
| // Try running your application with "flutter run". You'll see the |
| // application has a blue toolbar. Then, without quitting the app, try |
| // changing the primarySwatch below to Colors.green and then invoke |
| // "hot reload" (press "r" in the console where you ran "flutter run", |
| // or simply save your changes to "hot reload" in a Flutter IDE). |
| // Notice that the counter didn't reset back to zero; the application |
| // is not restarted. |
| primarySwatch: Colors.blue, |
| ), |
| home: const MyHomePage(title: 'Flutter Demo Home Page'), |
| ); |
| } |
| } |
| |
| class MyHomePage extends StatefulWidget { |
| const MyHomePage({super.key, this.title}); |
| |
| // This widget is the home page of your application. It is stateful, meaning |
| // that it has a State object (defined below) that contains fields that affect |
| // how it looks. |
| |
| // This class is the configuration for the state. It holds the values (in this |
| // case the title) provided by the parent (in this case the App widget) and |
| // used by the build method of the State. Fields in a Widget subclass are |
| // always marked "final". |
| |
| final String? title; |
| |
| @override |
| State<MyHomePage> createState() => _MyHomePageState(); |
| } |
| |
| class _MyHomePageState extends State<MyHomePage> { |
| int _counter = 0; |
| |
| void _incrementCounter() { |
| setState(() { |
| // This call to setState tells the Flutter framework that something has |
| // changed in this State, which causes it to rerun the build method below |
| // so that the display can reflect the updated values. If we changed |
| // _counter without calling setState(), then the build method would not be |
| // called again, and so nothing would appear to happen. |
| _counter++; |
| }); |
| } |
| |
| @override |
| Widget build(BuildContext context) { |
| // This method is rerun every time setState is called, for instance as done |
| // by the _incrementCounter method above. |
| // |
| // The Flutter framework has been optimized to make rerunning build methods |
| // fast, so that you can just rebuild anything that needs updating rather |
| // than having to individually change instances of widgets. |
| return Scaffold( |
| appBar: AppBar( |
| // Here we take the value from the MyHomePage object that was created by |
| // the App.build method, and use it to set our appbar title. |
| title: Text(widget.title ?? ''), |
| ), |
| body: Center( |
| // Center is a layout widget. It takes a single child and positions it |
| // in the middle of the parent. |
| child: Column( |
| // Column is also a layout widget. It takes a list of children and |
| // arranges them vertically. By default, it sizes itself to fit its |
| // children horizontally, and tries to be as tall as its parent. |
| // |
| // Invoke "debug painting" (press "p" in the console, choose the |
| // "Toggle Debug Paint" action from the Flutter Inspector in Android |
| // Studio, or the "Toggle Debug Paint" command in Visual Studio Code) |
| // to see the wireframe for each widget. |
| // |
| // Column has various properties to control how it sizes itself and |
| // how it positions its children. Here we use mainAxisAlignment to |
| // center the children vertically; the main axis here is the vertical |
| // axis because Columns are vertical (the cross axis would be |
| // horizontal). |
| mainAxisAlignment: MainAxisAlignment.center, |
| children: <Widget>[ |
| const Text( |
| 'You have pushed the button this many times:', |
| ), |
| Text( |
| '$_counter', |
| style: Theme.of(context).textTheme.headlineMedium, |
| ), |
| ], |
| ), |
| ), |
| floatingActionButton: FloatingActionButton( |
| onPressed: _incrementCounter, |
| tooltip: 'Increment', |
| child: const Icon(Icons.add), |
| ), // This trailing comma makes auto-formatting nicer for build methods. |
| ); |
| } |
| } |