Flutter中InheritedWidget相关

2019-09-11 14:21:09

import 'package:flutter/material.dart';

/// Inherited动画相关

class Inherited extends StatefulWidget {
  @override
  State<StatefulWidget> createState() {
    return new _InheritedState();
  }
}

class _InheritedState extends State<Inherited> {
  _InheritedState() {}

  @override
  void initState() {
    _counterData = new CounterData(101);
    super.initState();
  }

  CounterData _counterData;
  String _content = '默认值';
  int index = 1;

  _increase() {
    print('+++');
    setState(() {
      _counterData = new CounterData(_counterData.count + 1);
    });
  }

  _reduce() {
    print('---');
    setState(() {
      _counterData = new CounterData(_counterData.count - 1);
    });
  }

  @override
  Widget build(BuildContext context) {
    return new MyInheritedWidget(
        counterData: _counterData,
        reduce: _reduce,
        increase: _increase,
        content: _content,
        child: new Scaffold(
          appBar: new AppBar(
            title: new Text('Inherited动画'),
          ),
          body: _body(),
          floatingActionButton: new FloatingActionButton(
            onPressed: () {
              setState(() {
                _content = '${_content} --- ${index}';
                index++;
              });
            },
            child: new Icon(Icons.refresh),
          ),
        ));
  }

  Widget _body() {
    return new Column(
      mainAxisAlignment: MainAxisAlignment.center,
      children: <Widget>[
        new IncreaseBtn(),
        new CounterText(),
        new ReduceBtn(),
        new CharmView(),
      ],
    );
  }
}

class CounterData {
  final int count;

  const CounterData(this.count);
}

class MyInheritedWidget extends InheritedWidget {
  final CounterData counterData;
  final Function() reduce;
  final Function() increase;
  final Widget child;
  final String content;

  MyInheritedWidget({
    Key key,
    @required this.counterData,
    @required this.reduce,
    @required this.increase,
    @required this.content,
    @required this.child,
  }) : super(key: key, child: child);

  static MyInheritedWidget of(BuildContext context) {
    return context.inheritFromWidgetOfExactType(MyInheritedWidget);
  }

  @override
  bool updateShouldNotify(MyInheritedWidget oldWidget) {
    bool needUpdate = (counterData != oldWidget.counterData) || (content != oldWidget.content);
    print('F1 updateShouldNotify needUpdate = $needUpdate');
    return needUpdate;
  }
}

class IncreaseBtn extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return new Padding(
      padding: EdgeInsets.symmetric(horizontal: 20, vertical: 6),
      child: new RaisedButton(
        onPressed: () {
          print('加加加 F = ${MyInheritedWidget.of(context).increase}');
          MyInheritedWidget.of(context).increase();
        },
        child: new Text('+'),
      ),
    );
  }
}

class CounterText extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return new Padding(
        padding: EdgeInsets.symmetric(horizontal: 20, vertical: 6),
        child: new Text(
            '当前数字是：${MyInheritedWidget.of(context).counterData.count}'));
  }
}

class ReduceBtn extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return new Padding(
      padding: EdgeInsets.symmetric(horizontal: 20, vertical: 6),
      child: new RaisedButton(
        onPressed: () {
          MyInheritedWidget.of(context).reduce();
        },
        child: new Text('-'),
      ),
    );
  }
}

class CharmView extends StatefulWidget {
  @override
  State<StatefulWidget> createState() {
    return new _CharmViewState();
  }
}

class _CharmViewState extends State<CharmView> {
  @override
  void initState() {
    print('F1 initState');
    super.initState();
  }

  @override
  void didChangeDependencies() {
    print('F1 didChangeDependencies');
    super.didChangeDependencies();
  }

  @override
  void didUpdateWidget(CharmView oldWidget) {
    print('F1 didUpdateWidget');
    super.didUpdateWidget(oldWidget);
  }

  @override
  void deactivate() {
    super.deactivate();
  }

  @override
  void dispose() {
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return new Container(
       200,
      height: 100,
      alignment: Alignment.center,
      child: new Text(MyInheritedWidget.of(context).content),
    );
  }
}