Flutter 状态管理

前置知识 Mixin 概念
https://juejin.im/post/5bb204d3e51d450e4f38e2f6

build
https://juejin.im/post/5c665cb651882562914ec153

key
https://blog.csdn.net/weixin_43901866/article/details/88980514

状态管理文章
https://juejin.im/post/5de1dd446fb9a071817bfc6e
https://juejin.im/post/5d00a84fe51d455a2f22023f
https://www.bilibili.com/video/av65343050?p=10

不使用 model 的传值

祖组件将构造函数与count直接传给子组件而不通过中间的父组件

import 'package:flutter/material.dart';
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.yellow,
      ),
      home: MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}
class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);
  final String title;
  @override
  _MyHomePageState createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
  int _counter = 0;
  void _incrementCounter() {
    setState(() {
      _counter++;
    });
  }
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: CounterProvider(
        child: Swaper(),
        count: _counter,
        increaseCount: _incrementCounter,
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: _incrementCounter,
        tooltip: 'Increment',
        child: Icon(Icons.add),
      ), // This trailing comma makes auto-formatting nicer for build methods.
    );
  }
}
class Swaper extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Container(
      child: Counter(),
    );
  }
}
class Counter extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    final int count = CounterProvider.of(context).count;
    final VoidCallback increaseCount =
        CounterProvider.of(context).increaseCount;
    return ActionChip(
      label: Text("$count"),
      onPressed: increaseCount,
    );
  }
}
class CounterProvider extends InheritedWidget {
  final int count;
  final VoidCallback increaseCount;
  final Widget child;
  CounterProvider({this.count, this.increaseCount, this.child})
      : super(child: child);
  static CounterProvider of(BuildContext context) =>
      context.inheritFromWidgetOfExactType(CounterProvider);
  @override
  bool updateShouldNotify(InheritedWidget oldWidget) {
    // TODO: implement updateShouldNotify
    return true;
  }
}