Flutter TabBarView和BottomNavigationBar页面不会使用SetState刷新

import 'package:flutter/material.dart';

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

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

  List<Widget> _pages = [
    Page1(),
    Page2(),
    Page3(),
  ];

  void _onTabTapped(int index) {
    setState(() {
      _currentIndex = index;
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('TabBarView and BottomNavigationBar'),
      ),
      body: _pages[_currentIndex],
      bottomNavigationBar: BottomNavigationBar(
        currentIndex: _currentIndex,
        onTap: _onTabTapped,
        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',
          ),
        ],
      ),
    );
  }
}

class Page1 extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Center(
      child: Text('Page 1'),
    );
  }
}

class Page2 extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Center(
      child: Text('Page 2'),
    );
  }
}

class Page3 extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Center(
      child: Text('Page 3'),
    );
  }
}