从父 Stateful 小部件调用子 Stateful 上的 setState答案

【问题标题】：Invoking setState on child Stateful from parent Stateful widget从父 Stateful 小部件调用子 Stateful 上的 setState
【发布时间】：2021-08-22 00:32:08
【问题描述】：

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任何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"),
      ),
    );
  }
}

【问题讨论】：

标签： flutter flutter-layout flutter-widget

【解决方案1】：

你可以传递改变初始化变量的函数。

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()),
          ],
        ),
      ),
    );
  }
}

然后在孩子中

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"),
      ),
    );
  }
}

【讨论】：