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 THIS: Try running your application with "flutter run". You'll see // the application has a purple toolbar. Then, without quitting the app, // try changing the seedColor in the colorScheme below to Colors.green // and then invoke "hot reload" (save your changes or press the "hot // reload" button in a Flutter-supported IDE, or press "r" if you used // the command line to start the app). // // Notice that the counter didn't reset back to zero; the application // state is not lost during the reload. To reset the state, use hot // restart instead. // // This works for code too, not just values: Most code changes can be // tested with just a hot reload. colorScheme: .fromSeed(seedColor: Colors.deepPurple), ), home: const MyHomePage(title: 'Flutter Demo Home Page'), ); } } class MyHomePage extends StatefulWidget { const MyHomePage({super.key, required 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( // TRY THIS: Try changing the color here to a specific color (to // Colors.amber, perhaps?) and trigger a hot reload to see the AppBar // change color while the other colors stay the same. backgroundColor: Theme.of(context).colorScheme.inversePrimary, // 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. // // 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). // // TRY THIS: Invoke "debug painting" (choose the "Toggle Debug Paint" // action in the IDE, or press "p" in the console), to see the // wireframe for each widget. mainAxisAlignment: .center, children: [ 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), ), ); } }

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