Flutter StatefulWidget传递数据，多级控件传递数据

父类传递给子类可以通过构造方法。

那么子类给父类呢？

答案也是构造方法 直接传递VoidCallback进来

这个VoidCallback是通过查看onPress类型得到的

import 'package:flutter/material.dart';
 
class StateManagementDemo2 extends StatefulWidget {
  @override
  _StateManagement2State createState() => _StateManagement2State();
}
 
class _StateManagement2State extends State<StateManagementDemo2> {
  int _count = 0;
 
  void _increaseCount() {
    setState(() {
      _count += 1;
    });
  }
 
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text("StatueManagementDemo"),
        elevation: 0.0,
      ),
      body: Counter(_count, _increaseCount),
      floatingActionButton: FloatingActionButton(
        child: Icon(Icons.add),
        onPressed: () {
          setState(() {
            _count += 1;
          });
          print(_count);
        },
      ),
    );
  }
}
 
class Counter extends StatelessWidget {
  final int count;
  final VoidCallback increaseCount;
 
  Counter(this.count, this.increaseCount);
 
  @override
  Widget build(BuildContext context) {
    return Center(
      child: ActionChip(
        label: Text('$count'),
        onPressed: increaseCount,
      ),
    );
  }
}

多级别当然就是多个构造

import 'package:flutter/material.dart';
 
class StateManagementDemo3 extends StatefulWidget {
  @override
  _StateManagement3State createState() => _StateManagement3State();
}
 
class _StateManagement3State extends State<StateManagementDemo3> {
  int _count = 0;
 
  void _increaseCount() {
    setState(() {
      _count += 1;
    });
  }
 
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text("StatueManagementDemo"),
        elevation: 0.0,
      ),
      body: ConunterWrapper(_count, _increaseCount),
      floatingActionButton: FloatingActionButton(
        child: Icon(Icons.add),
        onPressed: () {
          setState(() {
            _count += 1;
          });
          print(_count);
        },
      ),
    );
  }
}
 
class ConunterWrapper extends StatelessWidget {
  final int count;
  final VoidCallback increaseCount;
 
  ConunterWrapper(this.count, this.increaseCount);
 
  @override
  Widget build(BuildContext context) {
    return Center(
      child: Counter(count, increaseCount),
    );
  }
}
 
class Counter extends StatelessWidget {
  final int count;
  final VoidCallback increaseCount;
 
  Counter(this.count, this.increaseCount);
 
  @override
  Widget build(BuildContext context) {
    return Center(
      child: ActionChip(
        label: Text('$count'),
        onPressed: increaseCount,
      ),
    );
  }
}