Flutter Popup Widget in a Provider -什么上下文将其弹出并关闭？

import 'package:flutter/material.dart';
import 'package:provider/provider.dart';

class MyPopupWidget extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return RaisedButton(
      child: Text('Open Popup'),
      onPressed: () {
        showDialog(
          context: context,
          builder: (BuildContext context) {
            return AlertDialog(
              title: Text('Popup Title'),
              content: Text('This is a popup.'),
              actions: <Widget>[
                FlatButton(
                  child: Text('Close'),
                  onPressed: () {
                    Navigator.of(context).pop();
                  },
                ),
              ],
            );
          },
        );
      },
    );
  }
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return ChangeNotifierProvider(
      create: (context) => MyProvider(),
      child: MaterialApp(
        home: Scaffold(
          appBar: AppBar(
            title: Text('My App'),
          ),
          body: Center(
            child: MyPopupWidget(),
          ),
        ),
      ),
    );
  }
}

class MyProvider with ChangeNotifier {
  // Provider state and methods go here
}

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