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| import 'package:flutter/material.dart'; | |
| /// | |
| /// Внешний виджет | |
| /// | |
| class ExternalWidget extends StatefulWidget { | |
| const ExternalWidget({Key? key}) : super(key: key); | |
| @override | |
| _ExternalWidgetState createState() => _ExternalWidgetState(); | |
| } | |
| class _ExternalWidgetState extends State<ExternalWidget> { | |
| // При инициализации виджета подписываемся на событие изменения | |
| // модели myModel. При изменении модели - обновляем ui | |
| @override | |
| void initState() { | |
| myModel.addListener(() { | |
| setState(() {}); | |
| }); | |
| super.initState(); | |
| } | |
| @override | |
| Widget build(BuildContext context) { | |
| return Scaffold( | |
| body: Center( | |
| child: Column( | |
| mainAxisAlignment: MainAxisAlignment.center, | |
| children: [ | |
| Text(myModel.foo), | |
| InternalWidget(), | |
| ], | |
| ), | |
| ), | |
| ); | |
| } | |
| } | |
| /// | |
| /// Внутренний виджет | |
| /// | |
| class InternalWidget extends StatefulWidget { | |
| const InternalWidget({Key? key}) : super(key: key); | |
| @override | |
| _InternalWidgetState createState() => _InternalWidgetState(); | |
| } | |
| class _InternalWidgetState extends State<InternalWidget> { | |
| // При инициализации виджета подписываемся на событие изменения | |
| // модели myModel. При изменении модели - обновляем ui | |
| @override | |
| void initState() { | |
| myModel.addListener(() { | |
| setState(() {}); | |
| }); | |
| super.initState(); | |
| } | |
| @override | |
| Widget build(BuildContext context) { | |
| return Column( | |
| children: [ | |
| Text(myModel.foo), | |
| ElevatedButton( | |
| onPressed: onPressed, | |
| child: Text('Изменить и текущий и вышестоящий виджет'), | |
| ), | |
| ], | |
| ); | |
| } | |
| void onPressed() { | |
| myModel.foo = 'changed'; | |
| } | |
| } | |
| /// | |
| /// Общая модель данных | |
| /// | |
| class MyModel with ChangeNotifier { | |
| String _foo = 'start value'; | |
| String get foo => _foo; | |
| set foo(String value) { | |
| _foo = value; | |
| // следующая функция оповестит слушателей о том, что состояние переменной изменилось | |
| notifyListeners(); | |
| } | |
| } | |
| final myModel = MyModel(); |
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