如何在flutter中创建圆角选项卡栏？

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: Text('圆角选项卡栏'),
        ),
        body: DefaultTabController(
          length: 3,
          child: Column(
            children: [
              Container(
                decoration: BoxDecoration(
                  borderRadius: BorderRadius.circular(20.0),
                  color: Colors.blue,
                ),
                child: TabBar(
                  indicator: BoxDecoration(
                    borderRadius: BorderRadius.circular(20.0),
                    color: Colors.white,
                  ),
                  tabs: [
                    Tab(text: '选项卡1'),
                    Tab(text: '选项卡2'),
                    Tab(text: '选项卡3'),
                  ],
                ),
              ),
              Expanded(
                child: TabBarView(
                  children: [
                    Center(child: Text('选项卡1的内容')),
                    Center(child: Text('选项卡2的内容')),
                    Center(child: Text('选项卡3的内容')),
                  ],
                ),
              ),
            ],
          ),
        ),
      ),
    );
  }
}