Flutter ListTile onTap函数不重定向到新页面

import 'package:flutter/material.dart';

class MyHomePage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Flutter ListTile'),
      ),
      body: ListView(
        children: <Widget>[
          ListTile(
            title: Text('Item 1'),
            onTap: () {
              Navigator.push(
                context,
                MaterialPageRoute(
                  builder: (context) => DetailPage(),
                ),
              );
            },
          ),
          ListTile(
            title: Text('Item 2'),
            onTap: () {
              Navigator.push(
                context,
                MaterialPageRoute(
                  builder: (context) => DetailPage(),
                ),
              );
            },
          ),
        ],
      ),
    );
  }
}

class DetailPage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Detail Page'),
      ),
      body: Center(
        child: Text('This is the detail page.'),
      ),
    );
  }
}

void main() {
  runApp(MaterialApp(
    home: MyHomePage(),
  ));
}