Flutter 使用provider记录

由于谷歌官方目前对provide停止了更新

现在采用的是Provider

首先导入包

import 'package:provider/provider.dart';

 

然后在Main函数中注册

void main(){
  runApp(
    MultiProvider(
      providers: [
        ChangeNotifierProvider(create: (_)=>Counter()),
        ChangeNotifierProvider(create: (_)=>ChildCategory()),
        ChangeNotifierProvider(create: (_)=>CategoryGoodsListProvider()),
        ChangeNotifierProvider(create: (_)=>DetailsInfoProvider()),
        ChangeNotifierProvider(create: (_)=>CartProvider())
      ],
      child: MyApp(),
    ),
  );
}

使用的时候会出现多种方式提供选择

第一种 使用 Provider.of 监听的地方记得把 listen设置为 true

 List cartList = Provider.of(context, listen: true).cartList;

在发送数据的界面 记得把listen设置为false

比如：

InkWell(){

onTap(){

Provider.of(context, listen: false).send(1);

}

}

 

第二种方式 用 官方代码如下：

// ignore_for_file: public_member_api_docs, lines_longer_than_80_chars
import 'package:flutter/foundation.dart';
import 'package:flutter/material.dart';
import 'package:provider/provider.dart';

/// This is a reimplementation of the default Flutter application using provider + [ChangeNotifier].

void main() {
  runApp(
    /// Providers are above [MyApp] instead of inside it, so that tests
    /// can use [MyApp] while mocking the providers
    MultiProvider(
      providers: [
        ChangeNotifierProvider(create: (_) => Counter()),
      ],
      child: MyApp(),
    ),
  );
}

/// Mix-in [DiagnosticableTreeMixin] to have access to [debugFillProperties] for the devtool
class Counter with ChangeNotifier, DiagnosticableTreeMixin {
  int _count = 0;
  int get count => _count;

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

  /// Makes `Counter` readable inside the devtools by listing all of its properties
  @override
  void debugFillProperties(DiagnosticPropertiesBuilder properties) {
    super.debugFillProperties(properties);
    properties.add(IntProperty('count', count));
  }
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return const MaterialApp(
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatelessWidget {
  const MyHomePage({Key key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('Example'),
      ),
      body: Center(
        child: Column(
          mainAxisSize: MainAxisSize.min,
          mainAxisAlignment: MainAxisAlignment.center,
          children: [
            const Text('You have pushed the button this many times:'),

            /// Extracted as a separate widget for performance optimization.
            /// As a separate widget, it will rebuild independently from [MyHomePage].
            ///
            /// This is totally optional (and rarely needed).
            /// Similarly, we could also use [Consumer] or [Selector].
            const Count(),
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        /// Calls `context.read` instead of `context.watch` so that it does not rebuild
        /// when [Counter] changes.
        onPressed: () => context.read().increment(),
        tooltip: 'Increment',
        child: const Icon(Icons.add),
      ),
    );
  }
}

class Count extends StatelessWidget {
  const Count({Key key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Text(

        /// Calls `context.watch` to make [MyHomePage] rebuild when [Counter] changes.
        '${context.watch().count}',
        style: Theme.of(context).textTheme.headline4);
  }
}

上面官方的代码使用了 

context.read().increment()；

和

context.watch().increment()；

一般read放到发送事件的地方比较好

watch一般用在接收数据的地方