请用Flutter实现一个底部有三个tab,每个tab上都有一个有app bar的页面的应用

首先，你需要在项目的pubspec.yaml文件中添加Flutter库。其次，在应用程序的主要文件中（通常是main.dart文件），您需要创建一个BottomNavigationBar来实现底部导航栏。接下来，在每个标签中创建一个新的页面，并在每个页面中添加AppBar。最后，在BottomNavigationBar的“onTap”回调中切换页面。示例代码如下：

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 _selectedIndex = 0;
  final List<Widget> _pages = [
    Page1(),
    Page2(),
    Page3(),
  ];

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('My App'),
      ),
      body: _pages[_selectedIndex],
      bottomNavigationBar: BottomNavigationBar(
        currentIndex: _selectedIndex,
        onTap: (int index) {
          setState(() {
            _selectedIndex = index;
          });
        },
        items: [
          BottomNavigationBarItem(
            icon: Icon(Icons.home),
            title: Text('Home'),
          ),
          BottomNavigationBarItem(
            icon: Icon(Icons.search),
            title: Text('Search'),
          ),
          BottomNavigationBarItem(
            icon: Icon(Icons.account_circle),
            title: Text('Profile'),
          ),
        ],
      ),
    );
  }
}

class Page1 extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Page 1'),
      ),
      body: Center(
        child: Text('This is Page 1'),
      ),
    );
  }
}

class Page2 extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Page 2'),