如何在Flutter中保持标签之间的状态(TabBar)？

class MyTabBar extends StatefulWidget {
  @override
  _MyTabBarState createState() => _MyTabBarState();
}

class _MyTabBarState extends State<MyTabBar> with SingleTickerProviderStateMixin {
  TabController _tabController;
  int _currentIndex = 0;

  @override
  void initState() {
    super.initState();
    _tabController = TabController(length: 2, vsync: this);
    _tabController.addListener(_handleTabChange);
  }

  void _handleTabChange() {
    setState(() {
      _currentIndex = _tabController.index;
    });
  }

  @override
  void dispose() {
    _tabController.dispose();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('My App'),
        bottom: TabBar(
          controller: _tabController,
          tabs: [
            Tab(
              text: 'Tab 1',
            ),
            Tab(
              text: 'Tab 2',
            ),
          ],
        ),
      ),
      body: TabBarView(
        controller: _tabController,
        children: [
          Tab1(),
          Tab2(),
        ],
      ),
    );
  }
}

class Tab1 extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Center(
      child: Text('Tab 1 Content'),
    );
  }
}

class Tab2 extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Center(
      child: Text('Tab 2 Content'),
    );
  }
}

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

class TabModel extends ChangeNotifier {
  int _currentIndex = 0;

  int get currentIndex => _currentIndex;

  void updateCurrentIndex(int index) {
    _currentIndex = index;
    notifyListeners();
  }
}

class MyTabBar extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return ChangeNotifierProvider<TabModel>(
      create: (context) => TabModel(),
      child: Scaffold(
        appBar: AppBar(
          title: Text('My App'),
          bottom: Consumer<TabModel>(
            builder: (context, model, _) => TabBar(
              tabs: [
                Tab(
                  text: 'Tab 1',
                ),
                Tab(
                  text: 'Tab 2',
                ),
              ],
              onTap: (index) => model.updateCurrentIndex(index),
            ),
          ),
        ),
        body: Consumer<TabModel>(
          builder: (context, model, _) => TabBarView(
            children: [
              Tab1(),
              Tab2(),
            ],
            controller: TabController(
              length: 2,
              initialIndex: model.currentIndex,
            ),
          ),
        ),
      ),
    );
  }
}

class Tab1 extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Center(
      child: Text('Tab 1 Content'),
    );
  }
}

class Tab2 extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Center(
      child: Text('Tab 2 Content'),
    );
  }
}

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