android-studio - 在flutter上对PopupMenuButton返回值方法使用setState方法

Question

如果我在另一个Dart文件中分离了一个小部件(PopupMenuButton)
我不能使用设置状态方法？

尽管PopupMenuButton是令人满意的小部件的子类
我不能使用setState？!

代码是:

PopupMenuButton<String> appBarMenu(BuildContext context, RateMyApp _rateMyApp) {
  return PopupMenuButton<String>(
      itemBuilder: (BuildContext context) {
        return choicesMenuBtn.map((String choice) {
          return PopupMenuItem<String>(
            child: Text('RateUS'),
          );
        }).toList();
      },
      onSelected: (val) {
        if (val == rateUsMenuBtn) {
          _rateMyApp.showStarRateDialog(
            context,
            actionsBuilder: (_, count) {
              final Widget cancelButton = RateMyAppNoButton(
                _rateMyApp,
                text: 'CANCEL',
                      //here is the problem
                callback: () => setState(() {}),
              );
            },
          );
        }
      });
}

Answer 1

state和setState方法仅在扩展StatefullWidget类的类内可用，您的代码是返回小部件的函数(方法)。因此，方法setState不可用。

一种解决方案是在您正在使用的statefullwidget中制作此方法

class Example extends StatefullWidet {
  @override
  createState() => _ExamleState();
}

class _ExampleState extends State<Example> {
 PopupMenuButton<String> appBarMenu(BuildContext context, RateMyApp _rateMyApp) {
  return PopupMenuButton<String>(
      itemBuilder: (BuildContext context) {
        return choicesMenuBtn.map((String choice) {
          return PopupMenuItem<String>(
            child: Text('RateUS'),
          );
        }).toList();
      },
      onSelected: (val) {
        if (val == rateUsMenuBtn) {
          _rateMyApp.showStarRateDialog(
            context,
            actionsBuilder: (_, count) {
              final Widget cancelButton = RateMyAppNoButton(
                _rateMyApp,
                text: 'CANCEL',
                      //here is the problem
                callback: () => setState(() {}),
              );
            },
          );
        }
      });
}

// other code inside the widget

}

或

如果您想在小部件中使用函数，则可以将函数用作参数

PopupMenuButton<String> appBarMenu(BuildContext context, RateMyApp _rateMyApp, Function onPress) {
  return PopupMenuButton<String>(
      itemBuilder: (BuildContext context) {
        return choicesMenuBtn.map((String choice) {
          return PopupMenuItem<String>(
            child: Text('RateUS'),
          );
        }).toList();
      },
      onSelected: (val) {
        if (val == rateUsMenuBtn) {
          _rateMyApp.showStarRateDialog(
            context,
            actionsBuilder: (_, count) {
              final Widget cancelButton = RateMyAppNoButton(
                _rateMyApp,
                text: 'CANCEL',
                      //here is the problem
                callback: onPress,
              );
            },
          );
        }
      });
}

// and whenever you call it you pass the onClick to the method.