flutter-状态管理-provider-3

关键代码

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  @override
  Widget build(BuildContext context) {
    final counter = CounterModel();
    const textSize = 30;
    return Provider<int>.value(
      value: textSize,
      child: ChangeNotifierProvider.value(
        value: counter,
        child: MaterialApp(
          title: 'Flutter Demo',
          theme: ThemeData(
            primarySwatch: Colors.blue,
          ),
          home: const MyHomePage(title: 'Flutter Demo Home Page'),
        ),
      ),
    );
  }
}

final counter = Provider.of<CounterModel>(context);
final textSize = Provider.of<int>(context).toDouble();

MultiProvider(
      providers: [ChangeNotifierProvider(create: (_) => CounterModel())],
      child: Scaffold(child: Text(
                counter.count.toString(),
                style: TextStyle(fontSize: textSize),
              ))
)

import 'package:flutter/foundation.dart';

class CounterModel with ChangeNotifier {
  int _count = 0;

  int get count => _count;

  void increment(){
    _count++;
    notifyListeners();
  }
}

import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
import 'model/counter.dart';
import 'page/home_page.dart';

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  @override
  Widget build(BuildContext context) {
    final counter = CounterModel();
    const textSize = 30;
    return Provider<int>.value(
      value: textSize,
      child: ChangeNotifierProvider.value(
        value: counter,
        child: 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) {
    final counter = Provider.of<CounterModel>(context);
    final textSize = Provider.of<int>(context).toDouble();

    return MultiProvider(
      providers: [ChangeNotifierProvider(create: (_) => CounterModel())],
      child: 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:',
              ),
              Text(
                counter.count.toString(),
                style: TextStyle(fontSize: textSize),
              ),
            ],
          ),
        ),
        floatingActionButton: FloatingActionButton(
          key: const Key('increment_floatingActionButton'),
          onPressed: () {
            counter.increment();
          },
          tooltip: 'Increment',
          child: const Icon(Icons.add),
        ), // This trailing comma makes auto-formatting nicer for build methods.
      ),
    );
  }
}

import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
import 'package:stream_demo/model/counter.dart';
import 'package:stream_demo/page/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) {
    final counter = Provider.of<CounterModel>(context);
    final textSize = Provider.of<int>(context).toDouble();
    return MultiProvider(
      providers: [ChangeNotifierProvider(create: (_) => CounterModel())],
      child: Scaffold(
        appBar: AppBar(
          title: Text(widget.title),
        ),
        body: Center(
          child: Column(
            mainAxisAlignment: MainAxisAlignment.center,
            children: [
              Text(
                counter.count.toString(),
                style: TextStyle(fontSize: textSize),
              ),
              //CountWidget(),
              FloatingActionButton(
                onPressed: () {
                  counter.increment();
                },
                tooltip: 'Increment',
                child: const Icon(Icons.add),
              )
            ],
          ),
        ), // This trailing comma makes auto-formatting nicer for build methods.
      ),
    );
  }
}