在Flutter中使用具有不同选项卡的不同FAB，并在它们之间滑动时更改按钮？

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: Text('FAB with Tabs Example'),
        ),
        body: MyTabs(),
      ),
    );
  }
}

class MyTabs extends StatefulWidget {
  @override
  _MyTabsState createState() => _MyTabsState();
}

class _MyTabsState extends State<MyTabs> with SingleTickerProviderStateMixin {
  int _currentIndex = 0;
  final List<Widget> _tabs = [
    Tab(icon: Icon(Icons.directions_car)),
    Tab(icon: Icon(Icons.directions_transit)),
    Tab(icon: Icon(Icons.directions_bike)),
  ];

  @override
  Widget build(BuildContext context) {
    return DefaultTabController(
      length: _tabs.length,
      child: Column(
        children: [
          TabBar(
            tabs: _tabs,
            onTap: (index) {
              setState(() {
                _currentIndex = index;
              });
            },
          ),
          Expanded(
            child: IndexedStack(
              index: _currentIndex,
              children: [
                CarTab(),
                TransitTab(),
                BikeTab(),
              ],
            ),
          ),
        ],
      ),
    );
  }
}

class CarTab extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Container(
      color: Colors.red,
      child: Center(child: Text('Car Tab')),
    );
  }
}

class TransitTab extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Container(
      color: Colors.green,
      child: Center(child: Text('Transit Tab')),
    );
  }
}

class BikeTab extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Container(
      color: Colors.blue,
      child: Center(child: Text('Bike Tab')),
    );
  }
}

class MyTabs extends StatefulWidget {
  @override
  _MyTabsState createState() => _MyTabsState();
}

class _MyTabsState extends State<MyTabs> with SingleTickerProviderStateMixin {
  int _currentIndex = 0;
  final List<Widget> _tabs = [
    Tab(icon: Icon(Icons.directions_car)),
    Tab(icon: Icon(Icons.directions_transit)),
    Tab(icon: Icon(Icons.directions_bike)),
  ];

  @override
  Widget build(BuildContext context) {
    return DefaultTabController(
      length: _tabs.length,
      child: Column(
        children: [
          TabBar(
            tabs: _tabs,
            onTap: (index) {
              setState(() {
                _currentIndex = index;
              });
            },
          ),
          Expanded(
            child: PageView.builder(
              itemCount: _tabs.length,
              onPageChanged: (index) {
                setState(() {
                  _currentIndex = index;
                });
              },
              itemBuilder: (context, index) {
                return index == 0 ? CarTab() : index == 1 ? TransitTab() : BikeTab();
              },
            ),
          ),
        ],
      ),
    );
  }
}

Scaffold(
  appBar: AppBar(
    title: Text('FAB with Tabs Example'),
  ),
  body: MyTabs(),
  floatingActionButton: FloatingActionButton(
    onPressed: () {
      // 根据 _currentIndex 执行相应的操作
    },
    child: Icon(_currentIndex == 0 ? Icons.directions_car : _currentIndex == 1 ? Icons.directions_transit : Icons.directions_bike),
  ),
);