如何在ModalRoute上使用setState()？

import 'package:flutter/material.dart';

class MyModalRoute extends StatefulWidget {
  @override
  _MyModalRouteState createState() => _MyModalRouteState();
}

class _MyModalRouteState extends State<MyModalRoute> {
  bool _isVisible = false;

  @override
  Widget build(BuildContext context) {
    return RaisedButton(
      child: Text('Show ModalRoute'),
      onPressed: () {
        setState(() {
          _isVisible = true;
        });
      },
    );
  }
  
  @override
  void dispose() {
    setState(() {
      _isVisible = false;
    });
    super.dispose();
  }
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: Text('ModalRoute Example'),
        ),
        body: Center(
          child: MyModalRoute(),
        ),
      ),
    );
  }
}

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