flutter的状态管理学习

import 'package:flutter/material.dart';

//material cupertino
//widget
//rendering
//foundation 动画 事件 painting
//flutter框架层
//engine
//embedded嵌入式

main() {
  runApp(const MaterialApp(
    home: StateStudyPage(),
  ));
}

class StateStudyPage extends StatefulWidget {
  const StateStudyPage({super.key});

  @override
  State<StateStudyPage> createState() => _StateStudyPageState();
}

class _StateStudyPageState extends State<StateStudyPage> {
  int aa = 0;

  int dt1 = 0;
  int dt2 = 0;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(),
      body: ShareData2Widget(
        dt1: dt1,
        dt2: dt2,
        child: Column(
          children: [
            Text("parent=$aa"),
            TextButton(
                onPressed: () {
                  setState(() {
                    aa++;
                  });
                },
                child: Text("刷新当前state")),
            TextButton(
                onPressed: () {
                  setState(() {
                    dt1++;
                  });
                },
                child: Text("刷新当前state dt1=$dt1")),
            TextButton(
                onPressed: () {
                  setState(() {
                    dt2++;
                  });
                },
                child: Text("刷新当前state dt2=$dt2")),
            StateStudyChildPage(
              aa: aa,
            ),
          ],
        ),
      ),
    );
  }
}

class StateStudyChildPage extends StatefulWidget {
  final int aa;

  const StateStudyChildPage({super.key, required this.aa});

  @override
  State<StateStudyChildPage> createState() => _StateStudyChildPageState();
}

class _StateStudyChildPageState extends State<StateStudyChildPage> {
  int a = 0;

  ///由于父widget setState 导致该方法调用
  @override
  void didUpdateWidget(covariant StateStudyChildPage oldWidget) {
    super.didUpdateWidget(oldWidget);
    print("更新widget");
  }

  ///由于用到了共享数据，并在数据变化的时候调用了父组件的setState，导致该方法调用
  @override
  void didChangeDependencies() {
    super.didChangeDependencies();
    print("依赖变化");
  }

  @override
  Widget build(BuildContext context) {
    return Column(
      children: [
        Text("child=$a"),
        Text("child==aa=${widget.aa}"),
        Text("child==cc=${ShareData2Widget.of(context, "data")?.dt1}"),
        TextButton(
            onPressed: () {
              setState(() {
                a++;
              });
            },
            child: Text("刷新当前state"))
      ],
    );
  }
}

///整体数据刷新
class ShareDataWidget extends InheritedWidget {
  const ShareDataWidget({
    super.key,
    required this.data,
    required super.child,
  });

  final int data; //需要在子树中共享的数据，保存点击次数

  //定义一个便捷方法，方便子树中的widget获取共享数据
  static ShareDataWidget? of(BuildContext context) {
    return context.dependOnInheritedWidgetOfExactType<ShareDataWidget>();
  }

  //该回调决定当data发生变化时，是否通知子树中依赖data的Widget重新build
  @override
  bool updateShouldNotify(ShareDataWidget oldWidget) {
    return oldWidget.data != data;
  }
}

///局部数据导致刷新
class ShareData2Widget extends InheritedModel<String> {
  const ShareData2Widget({
    super.key,
    required this.dt2,
    required this.dt1,
    required super.child,
  });

  final int dt1;
  final int dt2;

  //定义一个便捷方法，方便子树中的widget获取共享数据
  //type就是根据type来判断是否需要刷新组件
  static ShareData2Widget? of(BuildContext context, String type) {
    return context.dependOnInheritedWidgetOfExactType<ShareData2Widget>(
        aspect: type);
  }

  //该回调决定当data发生变化时，是否通知子树中依赖data的Widget重新build
  @override
  bool updateShouldNotify(ShareData2Widget oldWidget) {
    print("oldWidget.dt1 != dt1=${oldWidget.dt1 != dt1}");
    return oldWidget.dt1 != dt1 || oldWidget.dt2 != dt2;
  }

  @override
  bool updateShouldNotifyDependent(
      covariant ShareData2Widget oldWidget, Set<String> dependencies) {
    return dependencies.contains("data") && oldWidget.dt1 != dt1 ||
        dependencies.contains("data2") && oldWidget.dt2 != dt2;
  }
}