main.dart 4.3 KB

123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112
  1. import 'package:flutter/material.dart';
  2. void main() => runApp(const MyApp());
  3. class MyApp extends StatelessWidget {
  4. const MyApp({Key? key}) : super(key: key);
  5. // This widget is the root of your application.
  6. @override
  7. Widget build(BuildContext context) {
  8. return MaterialApp(
  9. title: 'Flutter Demo',
  10. theme: ThemeData(
  11. // This is the theme of your application.
  12. //
  13. // Try running your application with "flutter run". You'll see the
  14. // application has a blue toolbar. Then, without quitting the app, try
  15. // changing the primarySwatch below to Colors.green and then invoke
  16. // "hot reload" (press "r" in the console where you ran "flutter run",
  17. // or press Run > Flutter Hot Reload in a Flutter IDE). Notice that the
  18. // counter didn't reset back to zero; the application is not restarted.
  19. primarySwatch: Colors.blue,
  20. ),
  21. home: const MyHomePage(title: 'Flutter Demo Home Page'),
  22. );
  23. }
  24. }
  25. class MyHomePage extends StatefulWidget {
  26. const MyHomePage({Key? key, required this.title}) : super(key: key);
  27. // This widget is the home page of your application. It is stateful, meaning
  28. // that it has a State object (defined below) that contains fields that affect
  29. // how it looks.
  30. // This class is the configuration for the state. It holds the values (in this
  31. // case the title) provided by the parent (in this case the App widget) and
  32. // used by the build method of the State. Fields in a Widget subclass are
  33. // always marked "final".
  34. final String title;
  35. @override
  36. State<MyHomePage> createState() => _MyHomePageState();
  37. }
  38. class _MyHomePageState extends State<MyHomePage> {
  39. int _counter = 0;
  40. void _incrementCounter() {
  41. setState(() {
  42. // This call to setState tells the Flutter framework that something has
  43. // changed in this State, which causes it to rerun the build method below
  44. // so that the display can reflect the updated values. If we changed
  45. // _counter without calling setState(), then the build method would not be
  46. // called again, and so nothing would appear to happen.
  47. _counter++;
  48. });
  49. }
  50. @override
  51. Widget build(BuildContext context) {
  52. // This method is rerun every time setState is called, for instance as done
  53. // by the _incrementCounter method above.
  54. //
  55. // The Flutter framework has been optimized to make rerunning build methods
  56. // fast, so that you can just rebuild anything that needs updating rather
  57. // than having to individually change instances of widgets.
  58. return Scaffold(
  59. appBar: AppBar(
  60. // Here we take the value from the MyHomePage object that was created by
  61. // the App.build method, and use it to set our appbar title.
  62. title: Text(widget.title),
  63. ),
  64. body: Center(
  65. // Center is a layout widget. It takes a single child and positions it
  66. // in the middle of the parent.
  67. child: Column(
  68. // Column is also a layout widget. It takes a list of children and
  69. // arranges them vertically. By default, it sizes itself to fit its
  70. // children horizontally, and tries to be as tall as its parent.
  71. //
  72. // Invoke "debug painting" (press "p" in the console, choose the
  73. // "Toggle Debug Paint" action from the Flutter Inspector in Android
  74. // Studio, or the "Toggle Debug Paint" command in Visual Studio Code)
  75. // to see the wireframe for each widget.
  76. //
  77. // Column has various properties to control how it sizes itself and
  78. // how it positions its children. Here we use mainAxisAlignment to
  79. // center the children vertically; the main axis here is the vertical
  80. // axis because Columns are vertical (the cross axis would be
  81. // horizontal).
  82. mainAxisAlignment: MainAxisAlignment.center,
  83. children: <Widget>[
  84. const Text(
  85. 'You have pushed the button this many times:',
  86. ),
  87. Text(
  88. '$_counter',
  89. style: Theme.of(context).textTheme.headline4,
  90. ),
  91. ],
  92. ),
  93. ),
  94. floatingActionButton: FloatingActionButton(
  95. onPressed: _incrementCounter,
  96. tooltip: 'Increment',
  97. child: const Icon(Icons.add),
  98. ), // This trailing comma makes auto-formatting nicer for build methods.
  99. );
  100. }
  101. }