这个应该能用

使用插件：

tab_indicator_styler: ^2.0.0参考插件Here

import 'package:tab_indicator_styler/tab_indicator_styler.dart'

Row(
      children: [
        Expanded(
          child: TabBar(
            controller: _controller,
            isScrollable: true,
            labelColor: Colors.white,
            unselectedLabelColor: Colors.grey,
            indicatorColor: Colors.green,
            indicator: MaterialIndicator(
              color: Colors.blue,
              height: 5,
              topLeftRadius: 10,
              topRightRadius: 10,
              bottomLeftRadius: 0,
              bottomRightRadius: 0,
              tabPosition: TabPosition.bottom,
            ),
            indicatorSize: TabBarIndicatorSize.tab,
            indicatorWeight: 5.0,
            tabs: const [
              Tab(
                child: Text('Tab 1'),
              ),
              Tab(
                child: Text('Tab 2'),
              ),
              Tab(
                child: Text('Tab 3'),
              ),
              Tab(
                child: Text('Tab 4'),
              ),
            ],
          ),
        ),
      ],
    ),

输出

尝试添加indicator参数：

indicator: UnderlineTabIndicator(
          borderSide: BorderSide(width: 5.0),
          insets: EdgeInsets.symmetric(horizontal:16.0)
        ),

或者，您可以将选项卡放置在具有底部边框的Container小部件中。