ValueListenableBuilder 处理 Map扑

Question

我想从数据声明之外的小部件修改数据 (Map)。例如：

  class Home extends StatefulWidget {
    //...some code
    Map<int,String> myMap = {0:"Hi"};
    //...rest of the class

Home 的新子页面：

class Menu extends StatefulWidget {
//...some code
myMap.clear();
//...rest of the class

我该怎么做？我正在阅读有关 ValueListenableBuilder 的内容，这对我有帮助吗？显然，在 clear() 调用后，Home 内的 Map 应该为空。

Answer 1

您可以在此处使用功能检查。

class HomePage extends StatelessWidget {
   HomePage();

  Map<int,String> myMap = {0:"Hi"};
  
  void onCalledFromOutside() {
    print("befor clear value");
    print(myMap);
    
    myMap.clear();
      print("after clear value");
    print(myMap);
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
    child: ElevatedButton(
          onPressed: () { Navigator.of(context).push(
             MaterialPageRoute(
               builder: (context) => AnotherPage(onCalledFromOutside),
             ));
                        },
          child: const Text("Go to AnotherPage"),
        ),
      ),
    );
  }
}

class AnotherPage extends StatelessWidget {
  final Function callback;

  const AnotherPage(this.callback);

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
    child: ElevatedButton(
           onPressed: callback as VoidCallback,
           child:const Text("Press me to clear Map"),
        ),
      ),
    );
  }
}