myapp.dart

import 'dart:async';

import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import 'screens/style.dart';
import 'screens/home/home.dart';
import 'screens/gallery/gallery.dart';
import 'screens/settings/settings.dart';

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

class MyAppState extends State<MyApp> with SingleTickerProviderStateMixin {
  static const platform = const MethodChannel('com.examples.lessonone/battery');

  TabController tabController;
  PageController pageController;
  TabItem _tabHandler;

  var _title_app = null;
  int _tab = 0;

  @override
  void initState() {
    // TODO: implement initState
    super.initState();

    pageController = new PageController();
    tabController = new TabController(
      length: 3,
      vsync: this,
      initialIndex: 0,
    );

    _tabHandler = TabItems[0];
    tabController.addListener(listenerForTabChange);
    this._title_app = TabItems[0].title;
  }

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

  @override
  Widget build(BuildContext context) {
     //TODO: implement build
    return new Scaffold(
      appBar: new AppBar(
        title: new Text(_tabHandler.title),
        //new Text('Dailies Food'),
        backgroundColor: appColor,
        bottom: new TabBar(
          controller: tabController,
          indicatorColor: Colors.white,
          tabs: <Tab>[
            new Tab(icon: new Icon(TabItems[0].icon)),
            new Tab(icon: new Icon(TabItems[1].icon)),
            new Tab(icon: new Icon(TabItems[2].icon)),
          ],
        ),

        actions: <Widget>[
          new Icon(Icons.search),
          new Padding(padding: const EdgeInsets.symmetric(horizontal: 5.0)),
          new Icon(Icons.more_vert)
        ],
      ),

      body: new TabBarView(
        controller: tabController,
        children: <Widget>[
          new HomePage(),
          new GalleryPage(),
          new SettingsPage()
        ],
      ),
    );
  }

  // Get battery level.
  String _batteryLevel = 'Unknown battery level.';

  Future<String> _getBatteryLevel() async {
    String batteryLevel;
    try {
      final int result = await platform.invokeMethod('getBatteryLevel');
      batteryLevel = 'Battery level at $result % ';
    } on PlatformException catch (e) {
      batteryLevel = "Failed to get battery level: '${e.message}'.";
    }
    return batteryLevel;
  }

  void onTabChanged(int tab) {

    setState(() {
      this._tab = tab;
      this._title_app = TabItems[tab].title;
      print(_title_app);
    });
  }

  void listenerForTabChange() {
    onTabChanged(tabController.index);
    setState(() {
      _tabHandler = TabItems[tabController.index];
    });
  }
}

class TabItem {
  const TabItem({this.title, this.icon});
  final String title;
  final IconData icon;
}

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)
];