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myapp.dart

import 'package:flutter/material.dart';
import 'package:meta/meta.dart';

const List<TabItem> TabItems = const <TabItem>[
  const TabItem(title: 'Home', icon: Icons.home),
  const TabItem(title: 'Gallery', icon: Icons.image),
  const TabItem(title: 'Settings', icon: Icons.settings)
];

class MyApp extends StatefulWidget {
  @override
  MyAppState createState() => new MyAppState();
}

class MyAppState extends State<MyApp> with SingleTickerProviderStateMixin {
  TabController tabController;

  int _titleIndex = 0;

  @override
  void initState() {
    super.initState();

    tabController = new TabController(length: TabItems.length, vsync: this);
    tabController.animation.addListener(() {
      final titleIndex = tabController.animation.value.round();
      if (_titleIndex != titleIndex) {
        setState(() {
          _titleIndex = titleIndex;
        });
      }
    });
  }

  @override
  void dispose() {
    tabController.dispose();
    super.dispose();
  }

  void onIconPressed(String icon) {
    print('Icon $icon pressed.');
  }

  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      appBar: new AppBar(
        title: new Text(TabItems[_titleIndex].title),
        backgroundColor: Colors.blue,
        bottom: new TabBar(
          controller: tabController,
          indicatorColor: Colors.white,
          tabs: TabItems.map((item) => new Tab(icon: new Icon(item.icon))).toList(),
        ),
        actions: <Widget>[
          new IconButton(icon: new Icon(Icons.search), onPressed: () => onIconPressed('search')),
          new IconButton(icon: new Icon(Icons.more_vert), onPressed: () => onIconPressed('more')),
        ],
      ),
      body: new TabBarView(
        controller: tabController,
        children: <Widget>[
          new Container(alignment: Alignment.center, child: Text('Home')),
          new Container(alignment: Alignment.center, child: Text('Gallery')),
          new Container(alignment: Alignment.center, child: Text('Settings')),
        ],
      ),
    );
  }
}

class TabItem {
  const TabItem({@required this.title, @required this.icon});

  final String title;
  final IconData icon;
}