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首先是父组件

import 'package:flutter/material.dart';import 'package:testchuanzhi/Parent/ChildTwo.dart';import 'ChildOne.dart';// 传值class Parent extends StatefulWidget {
     @override  _ParentState createState() => _ParentState();}class _ParentState extends State
   
     {
     String data ='无';  String datatoParent ='来之父亲的问候';  void onDataChange(val) {
       setState(() {
         data = val;    });  }  @override  Widget build(BuildContext context) {
       return Container(      child: Center(        child: Column(            mainAxisAlignment: MainAxisAlignment.center,            children: 
    
     [              ChildOne(),              ChildTwo(datatoParent: datatoParent, callback: (val) => onDataChange(val)),              Container(                child: Text(data),              )            ],        ),      ),    );  }}
    
   

子组件

```kotlinimport 'package:flutter/material.dart';class ChildTwo extends StatefulWidget {
     ChildTwo({
   Key key, this.datatoParent, this.callback}) : super(key: key);  final callback;  String datatoParent;  @override  _ChildTwoState createState() => _ChildTwoState();}class _ChildTwoState extends State
   
     {
     String data ="来之父组件的问候";  void firedA() {
       print("子组件里面促发了点击");    widget.callback('$inputTxt');  }  String inputTxt;  @override  Widget build(BuildContext context) {
       return Container(      width: 100,      margin: EdgeInsets.only(top: 3),      child: Column(        children: 
    
     [          Container(            height: 20,            width: 100,            alignment: Alignment.center,            margin: EdgeInsets.only(top: 3.0),            decoration: BoxDecoration(                color: Colors.red, borderRadius: BorderRadius.circular(10.0)),            child:Text(widget.datatoParent),          ),          RaisedButton(            onPressed: firedA,            child: new Text('to父组件'),          ),          TextField(              decoration: const InputDecoration(                hintText: '给父组件传值',                contentPadding: const EdgeInsets.all(10.0),              ),              // 当监听的数值发生变化的时候 监听输入的数值              onChanged: (val) {
                   setState(() {
                     inputTxt = val;                });                print(inputTxt);              }),        ],      ),    );  }}
    
   

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