从父 Stateful 小部件调用子 Stateful 上的 setState

如何解决从父 Stateful 小部件调用子 Stateful 上的 setState

当我在子有状态小部件中调用 setState 时。它显示错误或警告。有没有什么方法可以在 Stateful 小部件中调用 Stateful 小部件而不会导致错误或有什么好的方法来做同样的事情？

这是我的示例代码：

parent.dart

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

class _ParentState extends State<Parent> {
  var title = "Parent";

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: SafeArea(
        child: ListView(
          children: <Widget>[
            Text(title),Child(init:true),// <-- Calling Child Widget
          ],),);
  }
}

child.dart

class Child extends StatefulWidget {
  final bool init;        // <- Showing warning on removing 'final' 
                         //  This class (or a class that this class inherits from) is marked as '@immutable',but one or more of its instance fields aren't final: Child.init

  Child({
    Key? key,required this.init,}) : super(key: key);
  @override
  _ChildState createState() => _ChildState();
}

class _ChildState extends State<Child> {
  @override
  Widget build(BuildContext context) {
    return Container(
      color: widget.init ? Colors.red : Colors.blue,child: TextButton(
        onPressed: () {
          setState(
            () {
              // widget.init = false;
              // want to change 'wiget.init' but its final
              // removing final causing warning
            },);
        },child: Text("Click me"),);
  }
}

解决方法

你可以传递改变init变量的函数。

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

class _ParentState extends State<Parent> {
  var title = "Parent";
  var init = true;

  void setInitFalse(){
      setState((){
        init = false;
      })
  }

bool getInit(){
         return init;
      }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: SafeArea(
        child: ListView(
          children: <Widget>[
            Text(title),Child(init: getInit(),setInitFalse: setInitFalse()),],),);
  }
}

然后在孩子

class Child extends StatefulWidget {
  final Function init;        // <- Showing warning on removing 'final' 
                         //  This class (or a class that this class inherits from) is marked as '@immutable',but one or more of its instance fields aren't final: Child.init
  final Function setInitFalse;

  Child({
    Key? key,required this.init,required this.setInitFalse
  }) : super(key: key);
  @override
  _ChildState createState() => _ChildState();
}

class _ChildState extends State<Child> {
  @override
  Widget build(BuildContext context) {
    return Container(
      color: widget.init() ? Colors.red : Colors.blue,child: TextButton(
        onPressed: () {
          widget.setInitFalse();
        },child: Text("Click me"),);
  }
}