如何从 Flutter 中的子小部件调用父小部件功能答案

【问题标题】：How to call parent widget function from child widget in Flutter如何从 Flutter 中的子小部件调用父小部件功能
【发布时间】：2021-05-04 04:38:10
【问题描述】：

我有一个父 StatefulWidget 和一个子 StatefulWidget。我想从子小部件调用父小部件的函数，即goToPreviousItem。

父类

class Parent extends StatefulWidget {
 @override
 _ParentState createState() => _ParentState();
 }

class _ParentState extends State<Parent> {
 String item = 0;
 @override
 Widget build(BuildContext context) {
   return ChildClass();
 }


goToPreviousItem(value){
 setState(() {item = value});
 }
}

儿童班

class Child extends StatefulWidget {
 @override
 _ChildState createState() => _ChildState();
 }

class _ChildState extends State<Child> {
 @override
 Widget build(BuildContext context) {
   return Container(
  child: FlatButton(
    color: Color(0XFFEFEFEF),
    textColor: primaryColor,
    disabledColor: Colors.grey,
    disabledTextColor: Colors.black,
    padding: EdgeInsets.symmetric(
        vertical: 15.0, horizontal: 10.0),
    onPressed: () => goToPreviousItem(2),
    child: Text(
      "Update",
    ),
  ),
);
   }
 }

我该怎么做？

【问题讨论】：

标签： flutter dart flutter-layout flutter-web

【解决方案1】：

在您的子小部件中创建一个Function 类型参数。

class Child extends StatefulWidget {

 Function function;
 Child({this.function});

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

class _ChildState extends State<Child> {
@override
Widget build(BuildContext context) {
 return Container(
child: FlatButton(
 color: Color(0XFFEFEFEF),
 textColor: primaryColor,
 disabledColor: Colors.grey,
 disabledTextColor: Colors.black,
 padding: EdgeInsets.symmetric(
     vertical: 15.0, horizontal: 10.0),
 onPressed: () => widget.function(2),
 child: Text(
   "Update",
         ),
      ),
    );
  }
}

将函数goToPreviousItem作为参数从父小部件传递给子小部件。
```
Child(function: goToPreviousItem);
```
在子窗口小部件中使用widget.function(2) 访问您的函数。

【讨论】：

【解决方案2】：

typedef parentFunctionCallback = void Function(String value);

class Parent extends StatefulWidget {
  @override
  _ParentState createState() => _ParentState();
}

class _ParentState extends State<Parent> {
  String item = 'data';
  
  @override
  Widget build(BuildContext context) {
    return ChildClass(goToPreviousItem);
  }
  
  goToPreviousItem(String value){
    setState(() {item = value;});
  }
}

class ChildClass extends StatefulWidget {
  const ChildClass(this.parentfunc);
  
  /// ToDo
  final parentFunctionCallback parentfunc; 
  
  @override
  _ChildState createState() => _ChildState();
}

class _ChildState extends State<ChildClass> {
  @override
  Widget build(BuildContext context) {
    return Container(
      child: FlatButton(
        color: Color(0XFFEFEFEF),
        textColor: primaryColor,
        disabledColor: Colors.grey,
        disabledTextColor: Colors.black,
        padding: EdgeInsets.symmetric(
            vertical: 15.0, horizontal: 10.0),
        onPressed: () => widget.parentfunc('mail'),
        child: Text(
          "Update",
        ),
      ),
    );
  }
}

【讨论】：