Flutter如何使用BottomNavigationBar管理独立的导航栈？

import 'package:flutter/material.dart';

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

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

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Flutter BottomNavigationBar'),
      ),
      body: IndexedStack(
        index: currentIndex,
        children: [
          // 页面1
          Container(
            color: Colors.red,
            child: Center(
              child: Text('Page 1'),
            ),
          ),
          // 页面2
          Container(
            color: Colors.green,
            child: Center(
              child: Text('Page 2'),
            ),
          ),
          // 页面3
          Container(
            color: Colors.blue,
            child: Center(
              child: Text('Page 3'),
            ),
          ),
        ],
      ),
      bottomNavigationBar: BottomNavigationBar(
        currentIndex: currentIndex,
        onTap: (index) {
          setState(() {
            currentIndex = index;
          });
        },
        items: [
          BottomNavigationBarItem(
            icon: Icon(Icons.home),
            label: 'Page 1',
          ),
          BottomNavigationBarItem(
            icon: Icon(Icons.business),
            label: 'Page 2',
          ),
          BottomNavigationBarItem(
            icon: Icon(Icons.school),
            label: 'Page 3',
          ),
        ],
      ),
    );
  }
}

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