如何让BottomNavigationBar响应通过AlertDialog导航到新页面？

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  int _currentIndex = 0;

  void _onItemTapped(int index) {
    showDialog(
      context: context,
      builder: (BuildContext context) {
        return AlertDialog(
          title: Text('导航确认'),
          content: Text('是否要导航到新页面？'),
          actions: [
            FlatButton(
              child: Text('取消'),
              onPressed: () {
                Navigator.of(context).pop();
              },
            ),
            FlatButton(
              child: Text('确认'),
              onPressed: () {
                Navigator.of(context).push(
                  MaterialPageRoute(
                    builder: (BuildContext context) => NewPage(),
                  ),
                );
              },
            ),
          ],
        );
      },
    );
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('BottomNavigationBar导航示例'),
      ),
      body: Center(
        child: Text('当前页面索引: $_currentIndex'),
      ),
      bottomNavigationBar: BottomNavigationBar(
        currentIndex: _currentIndex,
        onTap: _onItemTapped,
        items: [
          BottomNavigationBarItem(
            icon: Icon(Icons.home),
            label: '首页',
          ),
          BottomNavigationBarItem(
            icon: Icon(Icons.search),
            label: '搜索',
          ),
          BottomNavigationBarItem(
            icon: Icon(Icons.person),
            label: '个人',
          ),
        ],
      ),
    );
  }
}

class NewPage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('新页面'),
      ),
      body: Center(
        child: Text('这是一个新页面'),
      ),
    );
  }
}