class TabExample extends StatefulWidget {
  const TabExample({Key? key}) : super(key: key);

  @override
  _TabExampleState createState() => _TabExampleState();
}

class _TabExampleState extends State<TabExample> {
  int currentIndex = 0;

  @override
  Widget build(BuildContext context) {
    return DefaultTabController(
      length: 2,
      child: Builder(
        builder: (ctx) {
          final TabController tabController = DefaultTabController.of(ctx)!;
          tabController.addListener(() {
            if (!tabController.indexIsChanging) {
              setState(() => currentIndex = tabController.index);
            }
          });
          return Scaffold(
            appBar: AppBar(
              bottom: TabBar(
                tabs: [
                  Tab(icon: Text('Tab ONE')),
                  Tab(icon: Text('Tab TWO')),
                ],
              ),
              title: Text('Tabs Demo'),
            ),
            body: TabBarView(
              children: [
                _buildWidgetA(),
                _buildWidgetB(),
              ],
            ),
          );
        },
      ),
    );
  }

  Widget _buildWidgetA() {
    List<Widget> children = [];
    for (int i = 0; i < 20; i++) {
      children.add(
        Padding(
          padding: EdgeInsets.symmetric(vertical: 16),
          child: Container(
            height: 100,
            width: double.infinity,
            color: Colors.blue,
          ),
        ),
      );
    }
    return Scrollbar(
      isAlwaysShown: true,
      showTrackOnHover: true,
      child: SingleChildScrollView(
        primary: currentIndex == 0,
        child: Column(
          children: children,
        ),
      ),
    );
  }

  Widget _buildWidgetB() {
    List<Widget> children = [];
    for (int i = 0; i < 20; i++) {
      children.add(
        Padding(
          padding: EdgeInsets.symmetric(vertical: 16),
          child: Container(
            height: 100,
            width: double.infinity,
            color: Colors.green,
          ),
        ),
      );
    }
    return Scrollbar(
      isAlwaysShown: true,
      showTrackOnHover: true,
      child: SingleChildScrollView(
        primary: currentIndex == 1,
        child: Column(
          children: children,
        ),
      ),
    );
  }
}