showDialog 在 PopUpMenuButton onSelected 中有效，但在 PopUpMenuItem onTap 中无效

Question

我想知道为什么 showDialog 没有在稍微不同的上下文中显示，似乎在很多情况下，路线上的几层上下文不应阻止对话框的显示。特别是在显式传递导航器上下文时。以下是最小的可重复样本。我也尝试过使用

最终的全局密钥？导航键

并经过

navigatorKey.currentContext

到 showDialog 方法，这也不起作用。我知道这可能是因为 itemBuilder 中的上下文，但是有人对为什么 onTap 不会显示对话框有更好的解释吗？

import 'package:flutter/material.dart';

void main() {
  runApp(const MyApp());
}

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        colorScheme: ColorScheme.fromSeed(seedColor: Colors.deepPurple),
        useMaterial3: true,
      ),
      home: const MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({super.key, required this.title});
  final String title;
  @override
  State<MyHomePage> createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {

  @override
  Widget build(BuildContext context) {
    return Scaffold(

      body: Center(
          child:PopupMenuButton(
              icon: Icon(Icons.more_vert),
              onSelected: (value){
                if (value == "val1") {
                  // works
                  // showADialog(context);
                }
                if (value == "val2"){
                  showADialog(context);
                }
              },
              itemBuilder: (context) {
                return [
                  PopupMenuItem(
                      onTap: (){
                        // doesn't work
                        showADialog(context);
                      },
                      value: "val1",
                      child: Text("val1")),
                  PopupMenuItem(
                      value:"val2",
                      child: Text("val2"))
                ];
              })
      ), // This trailing comma makes auto-formatting nicer for build methods.
    );
  }
}

showADialog(BuildContext context){
  showDialog(
      context: context,
      builder: (context) {
    return AlertDialog(
        title: Text("A Dialog"));});
}

Answer 1

通过这种方式传递上下文；

return Scaffold(
          body: Center(
            child: PopupMenuButton<String>(
              icon: const Icon(Icons.more_vert),
              onSelected: (value) {
                if (value == "val2") {
                  showPopupDialog(context);
                }
              },
              itemBuilder: (context) {
                return [
                  PopupMenuItem(
                    value: "val1",
                    child: GestureDetector(
                      onTap: () => showPopupDialog(context), // Pass context here
                      child: const Text("val1"),
                    ),
                  ),
                  const PopupMenuItem(
                    value: "val2",
                    child: Text("val2"),
                  ),
                ];
              },
            ),
          ),
     );