前端学习-flutter学习-004-状态管理

《Flutter实战·第二版》

• Widget管理自身状态：自己继承StatefulWidget，自己内部设置变量（State）并进行管理
• 父Widget管理子Widget的状态：parent继承自StatefulWidget，设置变量及函数，传递给child；child继承自StatelessWidget
• 混合状态管理：既接受来自parent的变量和函数，自己继承自StatefulWidget，内部也管理参数（状态）
• 全局状态管理：需要一些跨组件（包括跨路由）的状态需要同步时（如设置应用的语言）

import 'package:flutter/material.dart';
import 'dart:ui';
  // import 'package:flutter/cupertino.dart';
  // void main() {
  //   runApp(const MyApp());
  // }
  
  void main() => runApp(const MyApp());
  // void main() => runApp(CupertinoApp(home: CupertinoTestRoute()));

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

  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        colorScheme: ColorScheme.fromSeed(seedColor: Colors.blue),
        useMaterial3: true,
      ),
      home:  HomePage(),
    );
  }
}


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

  @override
  Widget build(BuildContext context) {
    return Scaffold(
        appBar: AppBar(
        title: Text("Widget管理自身状态"),
          backgroundColor: Colors.green,
      ),
      body: Center(
        child: Column(
          children: [
            TapboxA(),
            ParentWidget(),
            ParentWidgetC(),
          ],
        ),
      ),
    );
    // return CounterWidget();
  }
}

// TapboxA 管理自身状态.
//------------------------- TapboxA ----------------------------------

class TapboxA extends StatefulWidget {
  TapboxA({Key? key}) : super(key: key);

  @override
  _TapboxAState createState() => _TapboxAState();
}

class _TapboxAState extends State<TapboxA> {
  bool _active = false;

  void _handleTap() {
    setState(() {
      _active = !_active;
    });
  }

  Widget build(BuildContext context) {
    return GestureDetector(
      onTap: _handleTap,
      child: Center(
        child: Container(
          child: Center(
            child: Text(
              _active ? 'Widget管理自身状态Active' : 'Widget管理自身状态Inactive',
              style: TextStyle(fontSize: 32.0, color: Colors.white),
            ),
          ),
          width: 200.0,
          height: 200.0,
          decoration: BoxDecoration(
            color: _active ? Colors.lightGreen[700] : Colors.grey[600],
          ),
        ),
      ),
    );
  }
}

// ParentWidget 为 TapboxB 管理状态.
//------------------------ ParentWidget --------------------------------

class ParentWidget extends StatefulWidget {
  @override
  _ParentWidgetState createState() => _ParentWidgetState();
}

class _ParentWidgetState extends State<ParentWidget> {
  bool _active = false;

  void _handleTapboxChanged(bool newValue) {
    setState(() {
      _active = newValue;
    });
  }

  @override
  Widget build(BuildContext context) {
    return Container(
      child: TapboxB(
        active: _active,
        onChanged: _handleTapboxChanged,
      ),
    );
  }
}

//------------------------- TapboxB ----------------------------------

class TapboxB extends StatelessWidget {
  TapboxB({Key? key, this.active = false, required this.onChanged})
      : super(key: key);

  final bool active;
  final ValueChanged<bool> onChanged;

  void _handleTap() {
    onChanged(!active);
  }

  Widget build(BuildContext context) {
    return GestureDetector(
      onTap: _handleTap,
      child: Container(
        child: Center(
          child: Text(
            active ? '父Widget管理子Widget的状态Active' : '父Widget管理子Widget的状态Inactive',
            style: TextStyle(fontSize: 32.0, color: Colors.white),
          ),
        ),
        width: 200.0,
        height: 200.0,
        decoration: BoxDecoration(
          color: active ? Colors.lightGreen[700] : Colors.grey[600],
        ),
      ),
    );
  }
}


// 混合状态管理
//---------------------------- ParentWidget ----------------------------

class ParentWidgetC extends StatefulWidget {
  @override
  _ParentWidgetCState createState() => _ParentWidgetCState();
}

class _ParentWidgetCState extends State<ParentWidgetC> {
  bool _active = false;

  void _handleTapboxChanged(bool newValue) {
    setState(() {
      _active = newValue;
    });
  }

  @override
  Widget build(BuildContext context) {
    return Container(
      child: TapboxC(
        active: _active,
        onChanged: _handleTapboxChanged,
      ),
    );
  }
}

//----------------------------- TapboxC ------------------------------

class TapboxC extends StatefulWidget {
  TapboxC({Key? key, this.active = false, required this.onChanged})
      : super(key: key);

  final bool active;
  final ValueChanged<bool> onChanged;

  @override
  _TapboxCState createState() => _TapboxCState();
}

class _TapboxCState extends State<TapboxC> {
  bool _highlight = false;

  void _handleTapDown(TapDownDetails details) {
    setState(() {
      _highlight = true;
    });
  }

  void _handleTapUp(TapUpDetails details) {
    setState(() {
      _highlight = false;
    });
  }

  void _handleTapCancel() {
    setState(() {
      _highlight = false;
    });
  }

  void _handleTap() {
    widget.onChanged(!widget.active);
  }

  @override
  Widget build(BuildContext context) {
    // 在按下时添加绿色边框，当抬起时，取消高亮
    return GestureDetector(
      onTapDown: _handleTapDown, // 处理按下事件
      onTapUp: _handleTapUp, // 处理抬起事件
      onTap: _handleTap,
      onTapCancel: _handleTapCancel,
      child: Container(
        child: Center(
          child: Text(
            widget.active ? '混合状态管理Active' : '混合状态管理Inactive',
            style: TextStyle(fontSize: 32.0, color: Colors.white),
          ),
        ),
        width: 200.0,
        height: 200.0,
        decoration: BoxDecoration(
          color: widget.active ? Colors.lightGreen[700] : Colors.grey[600],
          border: _highlight
              ? Border.all(
            color: Colors.teal,
            width: 10.0,
          )
              : null,
        ),
      ),
    );
  }
}