flutter/examples/api/lib/material/tab_controller/tab_controller.1.dart

// Copyright 2014 The Flutter Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

// Flutter code sample for [TabController].

import 'package:flutter/material.dart';

void main() => runApp(const MyApp());

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  static const String _title = 'Flutter Code Sample';

  @override
  Widget build(BuildContext context) {
    return const MaterialApp(
      title: _title,
      home: MyStatelessWidget(),
    );
  }
}

const List<Tab> tabs = <Tab>[
  Tab(text: 'Zeroth'),
  Tab(text: 'First'),
  Tab(text: 'Second'),
];

class MyStatelessWidget extends StatelessWidget {
  const MyStatelessWidget({super.key});

  @override
  Widget build(BuildContext context) {
    return DefaultTabController(
      length: tabs.length,
      // The Builder widget is used to have a different BuildContext to access
      // closest DefaultTabController.
      child: Builder(builder: (BuildContext context) {
        final TabController tabController = DefaultTabController.of(context);
        tabController.addListener(() {
          if (!tabController.indexIsChanging) {
            // Your code goes here.
            // To get index of current tab use tabController.index
          }
        });
        return Scaffold(
          appBar: AppBar(
            bottom: const TabBar(
              tabs: tabs,
            ),
          ),
          body: TabBarView(
            children: tabs.map((Tab tab) {
              return Center(
                child: Text(
                  '${tab.text!} Tab',
                  style: Theme.of(context).textTheme.headlineSmall,
                ),
              );
            }).toList(),
          ),
        );
      }),
    );
  }
}