如何在Flutter中从子类函数调用父类函数

沙鹿

我有一个家长班和一个孩子班。我想从子类调用父类的函数，即goToPreviousItem。

家长班

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",
    ),
  ),
);
   }
 }

我怎样才能做到这一点？

朝阳

Function在子类中创建一个类型参数。

将函数goToPreviousItem作为参数从父类传递到子类。

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.goToPreviousItem(2),
 child: Text(
   "Update",
         ),
      ),
    );
  }
}