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| import 'package:flutter/material.dart'; | |
| // This example showcases how by using functions instead of StatelessWidgets, | |
| // this can cause bugs when using InheritedWidgets | |
| void main() => runApp(MyApp()); | |
| class MyApp extends StatelessWidget { | |
| @override | |
| Widget build(context) { | |
| print('this build method is called only once'); | |
| return Counter( | |
| count: Count(), | |
| child: MaterialApp( | |
| home: Home(), | |
| // Uncomment to make your app crash | |
| // And if you fix the error, rebuilding the counter will rebuild MyApp | |
| // home: Scaffold( | |
| // body: Center( | |
| // child: Text('Count ${Counter.of(context).value}'), | |
| // ), | |
| // floatingActionButton: FloatingActionButton( | |
| // onPressed: () => Counter.of(context).value++, | |
| // child: Icon(Icons.add), | |
| // ), | |
| // ), | |
| ), | |
| ); | |
| } | |
| } | |
| class Count extends ValueNotifier<int> { | |
| Count() : super(0); | |
| } | |
| class Counter extends InheritedNotifier { | |
| Counter({ | |
| Key key, | |
| this.count, | |
| Widget child, | |
| }) : super(key: key, child: child, notifier: count); | |
| final Count count; | |
| static Count of(BuildContext context) { | |
| return context.dependOnInheritedWidgetOfExactType<Counter>().count; | |
| } | |
| } | |
| class Home extends StatelessWidget { | |
| @override | |
| Widget build(BuildContext context) { | |
| print('Home is re-executed without re-executing MyApp'); | |
| return Scaffold( | |
| body: Center( | |
| child: Text('Count ${Counter.of(context).value}'), | |
| ), | |
| floatingActionButton: FloatingActionButton( | |
| onPressed: () => Counter.of(context).value++, | |
| child: Icon(Icons.add), | |
| ), | |
| ); | |
| } | |
| } |
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