如何推送停留在Flutter BottomNavigationBar顶部的全屏页面

import 'package:flutter/material.dart';

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

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

class MainScreen extends StatefulWidget {
  @override
  _MainScreenState createState() => _MainScreenState();
}

class _MainScreenState extends State<MainScreen> {
  int _currentIndex = 0;

  final List<Widget> _pages = [
    HomeScreen(),
    NotificationsScreen(),
    ProfileScreen(),
  ];

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Flutter BottomNavigationBar'),
      ),
      body: _pages[_currentIndex],
      bottomNavigationBar: BottomNavigationBar(
        currentIndex: _currentIndex,
        onTap: (int index) {
          if (index == 1) {
            Navigator.push(
              context,
              MaterialPageRoute(builder: (context) => FullScreenPage()),
            );
          } else {
            setState(() {
              _currentIndex = index;
            });
          }
        },
        items: [
          BottomNavigationBarItem(
            icon: Icon(Icons.home),
            label: 'Home',
          ),
          BottomNavigationBarItem(
            icon: Icon(Icons.notifications),
            label: 'Notifications',
          ),
          BottomNavigationBarItem(
            icon: Icon(Icons.person),
            label: 'Profile',
          ),
        ],
      ),
    );
  }
}

class HomeScreen extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Center(
      child: Text('Home Screen'),
    );
  }
}

class NotificationsScreen extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Center(
      child: Text('Notifications Screen'),
    );
  }
}

class ProfileScreen extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Center(
      child: Text('Profile Screen'),
    );
  }
}

class FullScreenPage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Full Screen Page'),
      ),
      body: Container(
        color: Colors.white,
        child: Center(
          child: Text('This is a full screen page'),
        ),
      ),
    );
  }
}