关键代码
MultiProvider(
providers: [ChangeNotifierProvider(create: (_) => Counter())],
child: const MyApp(),
)
context.read<Counter>().increment();
context.watch<Counter>().count
counter.dart
import 'package:flutter/foundation.dart';
class Counter with ChangeNotifier, DiagnosticableTreeMixin {
int _count = 0;
int get count => _count;
void increment(){
_count++;
notifyListeners();
}
@override
void debugFillProperties(DiagnosticPropertiesBuilder properties) {
super.debugFillProperties(properties);
properties.add(IntProperty('count', count));
}
}
main.dart
import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
import 'package:stream_demo/model/counter.dart';
import 'my_app.dart';
void main() {
runApp(MultiProvider(
providers: [ChangeNotifierProvider(create: (_) => Counter())],
child: const MyApp(),
));
}
class MyApp extends StatelessWidget {
const MyApp({super.key});
@override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(
primarySwatch: Colors.blue,
),
home: const MyHomePage(title: 'Flutter Demo Home Page'),
);
}
}
import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
import 'package:stream_demo/model/counter.dart';
import 'detail_page.dart';
class MyHomePage extends StatefulWidget {
const MyHomePage({super.key, required this.title});
final String title;
@override
State<MyHomePage> createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text(widget.title),
),
body: Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
OutlinedButton(
onPressed: () {
Navigator.push(context, MaterialPageRoute(builder: (context) {
return const MyDetailPage(title: "我是详情页面");
}));
},
child: Text("详情页")),
const Text(
'You have pushed the button this many times:',
),
Count(),
],
),
),
floatingActionButton: FloatingActionButton(
key: const Key('increment_floatingActionButton'),
onPressed: () {
context.read<Counter>().increment();
},
tooltip: 'Increment',
child: const Icon(Icons.add),
), // This trailing comma makes auto-formatting nicer for build methods.
);
}
}
class Count extends StatelessWidget {
@override
Widget build(BuildContext context) {
return Text(
"${context.watch<Counter>().count}",
key: const Key('counterState'),
style: Theme.of(context).textTheme.headlineMedium,
);
}
}
import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
import 'package:stream_demo/model/counter.dart';
import 'home_page.dart';
class MyDetailPage extends StatefulWidget {
const MyDetailPage({super.key, required this.title});
final String title;
@override
State<MyDetailPage> createState() => _MyDetailPageState();
}
class _MyDetailPageState extends State<MyDetailPage> {
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text(widget.title),
),
body: Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: [
Count(),
FloatingActionButton(
onPressed: (){
context.read<Counter>().increment();
},
tooltip: 'Increment',
child: const Icon(Icons.add),
)
],
),
), // This trailing comma makes auto-formatting nicer for build methods.
);
}
}