you can use "container_tab_indicator" package
install it with flutter pub add container_tab_indicator
then use it like this:
import 'package:container_tab_indicator/container_tab_indicator.dart';
...
TabBar(
tabs: [
Text('Orders', style: TextStyle(color: Colors.pink[900])),
Text('Order Requests', style: TextStyle(color: Colors.pink[900])),
Text('My Requests', style: TextStyle(color: Colors.pink[900])),
],
indicator: ContainerTabIndicator(
//play with these properties as you see fit
radius: BorderRadius.all(Radius.circular(16.0)),
padding: const EdgeInsets.only(left: 36),
),
),