TabBar - custom ripple effect

main.dart

import 'package:flutter/material.dart';

void main() {
  runApp(TabBarDemo());
}

class TabBarDemo extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: DefaultTabController(
        length: 2,
        child: Scaffold(
          appBar: AppBar(
            bottom: PreferredSize(
              preferredSize: Size.fromHeight(40),
              child: Material(
                color: Colors.transparent,
                shape: RoundedRectangleBorder(
                  borderRadius: BorderRadius.circular(
                    20,
                  ),
                ),
                clipBehavior: Clip.antiAlias,
                child: TabBar(
                  tabs: [
                    Tab(icon: Icon(Icons.directions_car)),
                    Tab(icon: Icon(Icons.directions_transit)),
                  ],
                ),
              ),
            ),
            title: Text('Tabs Demo'),
          ),
          body: TabBarView(
            children: [
              Icon(Icons.directions_car),
              Icon(Icons.directions_transit),
            ],
          ),
        ),
      ),
    );
  }
}