main.dart 3.9 KB

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  1. import 'package:flutter/material.dart';
  2. void main() {
  3. runApp(const MyApp());
  4. }
  5. class MyApp extends StatelessWidget {
  6. const MyApp({super.key});
  7. // This widget is the root of your application.
  8. @override
  9. Widget build(BuildContext context) {
  10. return MaterialApp(
  11. title: 'Flutter Demo',
  12. theme: ThemeData(
  13. // This is the theme of your application.
  14. //
  15. // Try running your application with "flutter run". You'll see the
  16. // application has a blue toolbar. Then, without quitting the app, try
  17. // changing the primarySwatch below to Colors.green and then invoke
  18. // "hot reload" (press "r" in the console where you ran "flutter run",
  19. // or simply save your changes to "hot reload" in a Flutter IDE).
  20. // Notice that the counter didn't reset back to zero; the application
  21. // is not restarted.
  22. primarySwatch: Colors.blue,
  23. ),
  24. home: const MyHomePage(title: 'Flutter Demo Home Page'),
  25. );
  26. }
  27. }
  28. class MyHomePage extends StatefulWidget {
  29. const MyHomePage({super.key, required this.title});
  30. final String title;
  31. @override
  32. State<MyHomePage> createState() => _MyHomePageState();
  33. }
  34. class _MyHomePageState extends State<MyHomePage> {
  35. int _counter = 0;
  36. void _incrementCounter() {
  37. setState(() {
  38. // This call to setState tells the Flutter framework that something has
  39. // changed in this State, which causes it to rerun the build method below
  40. // so that the display can reflect the updated values. If we changed
  41. // _counter without calling setState(), then the build method would not be
  42. // called again, and so nothing would appear to happen.
  43. _counter++;
  44. });
  45. }
  46. @override
  47. Widget build(BuildContext context) {
  48. // This method is rerun every time setState is called, for instance as done
  49. // by the _incrementCounter method above.
  50. //
  51. // The Flutter framework has been optimized to make rerunning build methods
  52. // fast, so that you can just rebuild anything that needs updating rather
  53. // than having to individually change instances of widgets.
  54. return Scaffold(
  55. appBar: AppBar(
  56. // Here we take the value from the MyHomePage object that was created by
  57. // the App.build method, and use it to set our appbar title.
  58. title: Text(widget.title),
  59. ),
  60. body: Center(
  61. // Center is a layout widget. It takes a single child and positions it
  62. // in the middle of the parent.
  63. child: Column(
  64. // Column is also a layout widget. It takes a list of children and
  65. // arranges them vertically. By default, it sizes itself to fit its
  66. // children horizontally, and tries to be as tall as its parent.
  67. //
  68. // Invoke "debug painting" (press "p" in the console, choose the
  69. // "Toggle Debug Paint" action from the Flutter Inspector in Android
  70. // Studio, or the "Toggle Debug Paint" command in Visual Studio Code)
  71. // to see the wireframe for each widget.
  72. //
  73. // Column has various properties to control how it sizes itself and
  74. // how it positions its children. Here we use mainAxisAlignment to
  75. // center the children vertically; the main axis here is the vertical
  76. // axis because Columns are vertical (the cross axis would be
  77. // horizontal).
  78. mainAxisAlignment: MainAxisAlignment.center,
  79. children: <Widget>[
  80. const Text(
  81. 'You have pushed the button this many times:',
  82. ),
  83. Text(
  84. '$_counter',
  85. style: Theme.of(context).textTheme.headline4,
  86. ),
  87. ],
  88. ),
  89. ),
  90. floatingActionButton: FloatingActionButton(
  91. onPressed: _incrementCounter,
  92. tooltip: 'Increment',
  93. child: const Icon(Icons.add),
  94. ), // This trailing comma makes auto-formatting nicer for build methods.
  95. );
  96. }
  97. }