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main.dart 4.5KB

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  1. import 'package:flutter/material.dart';
  2. void main() {
  3. runApp(MyApp());
  4. }
  5. class MyApp extends StatelessWidget {
  6. // This widget is the root of your application.
  7. @override
  8. Widget build(BuildContext context) {
  9. return MaterialApp(
  10. title: 'Flutter Demo',
  11. theme: ThemeData(
  12. // This is the theme of your application.
  13. //
  14. // Try running your application with "flutter run". You'll see the
  15. // application has a blue toolbar. Then, without quitting the app, try
  16. // changing the primarySwatch below to Colors.green and then invoke
  17. // "hot reload" (press "r" in the console where you ran "flutter run",
  18. // or simply save your changes to "hot reload" in a Flutter IDE).
  19. // Notice that the counter didn't reset back to zero; the application
  20. // is not restarted.
  21. primarySwatch: Colors.blue,
  22. // This makes the visual density adapt to the platform that you run
  23. // the app on. For desktop platforms, the controls will be smaller and
  24. // closer together (more dense) than on mobile platforms.
  25. visualDensity: VisualDensity.adaptivePlatformDensity,
  26. ),
  27. home: MyHomePage(title: 'Flutter Demo Home Page'),
  28. );
  29. }
  30. }
  31. class MyHomePage extends StatefulWidget {
  32. MyHomePage({Key key, this.title}) : super(key: key);
  33. // This widget is the home page of your application. It is stateful, meaning
  34. // that it has a State object (defined below) that contains fields that affect
  35. // how it looks.
  36. // This class is the configuration for the state. It holds the values (in this
  37. // case the title) provided by the parent (in this case the App widget) and
  38. // used by the build method of the State. Fields in a Widget subclass are
  39. // always marked "final".
  40. final String title;
  41. @override
  42. _MyHomePageState createState() => _MyHomePageState();
  43. }
  44. class _MyHomePageState extends State<MyHomePage> {
  45. int _counter = 0;
  46. void _incrementCounter() {
  47. setState(() {
  48. // This call to setState tells the Flutter framework that something has
  49. // changed in this State, which causes it to rerun the build method below
  50. // so that the display can reflect the updated values. If we changed
  51. // _counter without calling setState(), then the build method would not be
  52. // called again, and so nothing would appear to happen.
  53. _counter++;
  54. });
  55. }
  56. @override
  57. Widget build(BuildContext context) {
  58. // This method is rerun every time setState is called, for instance as done
  59. // by the _incrementCounter method above.
  60. //
  61. // The Flutter framework has been optimized to make rerunning build methods
  62. // fast, so that you can just rebuild anything that needs updating rather
  63. // than having to individually change instances of widgets.
  64. return Scaffold(
  65. appBar: AppBar(
  66. // Here we take the value from the MyHomePage object that was created by
  67. // the App.build method, and use it to set our appbar title.
  68. title: Text(widget.title),
  69. ),
  70. body: Center(
  71. // Center is a layout widget. It takes a single child and positions it
  72. // in the middle of the parent.
  73. child: Column(
  74. // Column is also a layout widget. It takes a list of children and
  75. // arranges them vertically. By default, it sizes itself to fit its
  76. // children horizontally, and tries to be as tall as its parent.
  77. //
  78. // Invoke "debug painting" (press "p" in the console, choose the
  79. // "Toggle Debug Paint" action from the Flutter Inspector in Android
  80. // Studio, or the "Toggle Debug Paint" command in Visual Studio Code)
  81. // to see the wireframe for each widget.
  82. //
  83. // Column has various properties to control how it sizes itself and
  84. // how it positions its children. Here we use mainAxisAlignment to
  85. // center the children vertically; the main axis here is the vertical
  86. // axis because Columns are vertical (the cross axis would be
  87. // horizontal).
  88. mainAxisAlignment: MainAxisAlignment.center,
  89. children: <Widget>[
  90. Text(
  91. 'You have pushed the button this many times:',
  92. ),
  93. Text(
  94. '$_counter',
  95. style: Theme.of(context).textTheme.headline4,
  96. ),
  97. ],
  98. ),
  99. ),
  100. floatingActionButton: FloatingActionButton(
  101. onPressed: _incrementCounter,
  102. tooltip: 'Increment',
  103. child: Icon(Icons.add),
  104. ), // This trailing comma makes auto-formatting nicer for build methods.
  105. );
  106. }
  107. }