如何在appbar中自定义标签？

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('Custom AppBar'),
          bottom: PreferredSize(
            preferredSize: Size.fromHeight(48.0),
            child: Container(
              color: Colors.blue,
              child: TabBar(
                tabs: [
                  Tab(text: 'Tab 1'),
                  Tab(text: 'Tab 2'),
                  Tab(text: 'Tab 3'),
                ],
              ),
            ),
          ),
        ),
        body: TabBarView(
          children: [
            Center(child: Text('Tab 1 content')),
            Center(child: Text('Tab 2 content')),
            Center(child: Text('Tab 3 content')),
          ],
        ),
      ),
    );
  }
}