使用 PreferredSize

class TabBarTestView extends StatelessWidget {
  const TabBarTestView({super.key});

  @override
  Widget build(BuildContext context) {
    return DefaultTabController(
        initialIndex: 1,
        length: 2,
        child: Scaffold(
          appBar: const PreferredSize(
            preferredSize: Size.fromHeight(kToolbarHeight),
            child: TabBar(tabs: <Widget>[
              Tab(text: "Tab 1"),
              Tab(text: "Tab 2"),
            ]),
          ),
          body: TabBarView(
            children: [...],
          ),
        ));
  }
}