一个使用InheritedWidget的错误范例

inherited_widget_test.dart

import 'package:flutter/material.dart';

void main() {
  runApp(MaterialApp(
    home: Scaffold(
      body: MyWidget(),
    ),
  ));
}

class MyWidget extends StatefulWidget {
  @override
  State<StatefulWidget> createState() {
    return MyState();
  }
}

class MyState extends State<MyWidget> {
  int tmpData = 0;
  @override
  Widget build(BuildContext context) {
    print('MyWidget build');
    return MyInherited(
      data: tmpData,
      child: Container(
        child: Column(
          children: <Widget>[
            WidgetA(),
            WidgetB(),
            FlatButton(
              child: Text("Click me"),
              onPressed: () {
                setState(() {
                  print('onPressed');
                  tmpData += 1;
                });
              },
            ),
          ],
        ),
      ),
    );
  }
}

class MyInherited extends InheritedWidget {
  final int data;

  MyInherited({this.data, Widget child}) : super(child : child) {
    print('MyInherited construct');
  }

  @override
  bool updateShouldNotify(MyInherited oldWidget) {
    bool result = oldWidget.data != this.data;
    print('MyInherited updateShouldNotify result = $result');
    return result;
  }

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

class WidgetA extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    print('WidgetA build');
    int data = MyInherited.of(context).data;
    return Text('WidgetA data = $data');
  }
}

class WidgetB extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    print('WidgetB build');
    return Text('WidgetB');
  }
}