在我再次重新打开菜单之前，flutter 中的菜单操作中的复选框不会更新

Question

这里是代码的相关部分：

class QuestionsScreen extends StatefulWidget {
  @override
  QuestionsScreenState createState() => QuestionsScreenState();
}

    class QuestionsScreenState extends State<QuestionsScreen> {
      final List<Question> questions = [];
      bool offline = false;
    
      @override
      Widget build(BuildContext context) {
        return BlocProvider(
          create: (context) => QuestionsBloc(sl.get<QuestionsRepository>())
            ..add(QuestionsInitialLoad()),
          child: Scaffold(
            appBar: AppBar(
              title: Text('Whosebug Questions'),
              centerTitle: true,
              actions: <Widget>[
                PopupMenuButton<int>(
                    itemBuilder: (BuildContext context) => <PopupMenuItem<int>>[
                          new PopupMenuItem<int>(value: 1, child: Text('Refresh')),
                          new PopupMenuItem<int>(
                              value: 2,
                              child: new Row(children: <Widget>[
                                new Text("Offline"),
                                new Checkbox(
                                  value: offline,
                                  onChanged: (newValue) {
                                    setState(() {
                                      offline = newValue!;
                                    });
                                  }, //  <-- leading Checkbox
                                )
                              ])),
                        ],
                    onSelected: (int value) {
                      setState(() {
                        if (value == 1) {
                          questions.clear();
                          QuestionsBloc(sl.get<QuestionsRepository>())
                            ..add
                            ..isFetching = true
                            ..add(QuestionsRestart());
                        }
                      });
                    })
              ],
            ),
            body: QuestionsBody(questions, offline),
          ),
        );
      }
    }

如您所见，我在 flutter 中的脚手架应用栏的弹出菜单操作按钮内声明了一个复选框。当我点击它时，更新发生了，但是直到我再次重新打开菜单我才能看到更新。是否可以立即在弹出菜单中看到复选框的更新？谢谢

Answer 1

这是点击 PopupMenuButton

后在开发工具上的显示效果

PopupMenuItem 不在当前上下文中。

我们可以使用 StatefulBuilder 来处理这种情况，在这种情况下，将 CheckBox 换成 StatefulBuilder。您也可以选择 Row.

StatefulBuilder(
    builder: (context, setStateSB) => Checkbox(
          value: offline,
          onChanged: (newValue) {
            setStateSB(() {
              offline = newValue!; // to update checkbox
            });
            setState(() {
              offline = newValue!; //to update the main ui if needed
            });
          },
        )),

在我再次重新打开菜单之前，flutter 中的菜单操作中的复选框不会更新

Ckeckbox inside menu actions in flutter is not updated until I reopen the menu again

flutter

flutter-layout

flutter-bloc