Flutter中如何从子Widget调用父Widget的函数

Question

我有一个父状态组件和一个子状态组件。我想从子组件调用父组件的函数，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});
 }
}

子类

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",
    ),
  ),
);
   }
 }

我该如何做到这一点？

- shalu j

Answer 1

在您的子widget中创建一个Function类型的参数。

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作为参数从父部件传递到子部件。

Child(function: goToPreviousItem);

在子窗口中使用widget.function(2)即可访问您的函数。

- ASAD HAMEED

Answer 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",
        ),
      ),
    );
  }
}

- Balasubramani Sundaram