如何为flutter navigator.push a showModalBottomSheet？

import 'package:flutter/material.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Navigator and showModalBottomSheet',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: HomePage(),
    );
  }
}

class HomePage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Home'),
      ),
      body: Center(
        child: RaisedButton(
          child: Text('Open Next Page'),
          onPressed: () {
            Navigator.push(context, MaterialPageRoute(builder: (context) => NextPage()));
          },
        ),
      ),
    );
  }
}

class NextPage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Next Page'),
      ),
      body: Center(
        child: RaisedButton(
          child: Text('Show Modal Bottom Sheet'),
          onPressed: () {
            showModalBottomSheet(
              context: context,
              builder: (BuildContext context) {
                return Container(
                  height: 200,
                  color: Colors.white,
                  child: Center(
                    child: Text('This is a Modal Bottom Sheet'),
                  ),
                );
              },
            );
          },
        ),
      ),
    );
  }
}