Flutter 7.2 - TabBar & BottomNavigationBar

 1, Tab bar: 

class _TabScreenState extends State<TabScreen> {
  @override
  Widget build(BuildContext context) {
    return DefaultTabController(
        length: 2,  // số tab
        child: Scaffold(
          appBar: AppBar(
            title: Text('Meals'),
            bottom: TabBar(
              tabs: [
                Tab(
                  icon: Icon(Icons.category),
                  text: 'Category',
                ),
                Tab(
                  icon: Icon(Icons.star),
                  text: 'Favorites',
                ),
              ],
            ),
          ),
          body: TabBarView(
            children: [
              CategoriesScreen(),
              FavoritesScreen(),
            ],
          ),
        ));
  }
}

2, BottomNavigationBar

class _TabScreenState extends State<TabScreen> {
  final List<Map<String, Object>> _pages = [
    {'title': 'Categories', 'page': CategoriesScreen()},
    {'title': 'Favorites', 'page': FavoritesScreen()},
  ];
  int _selectedPageIndex = 0;

  void _selectPage(int index) {
    setState(() {
      _selectedPageIndex = index;
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(_pages[_selectedPageIndex]['title'] as String),
      ),
      body: _pages[_selectedPageIndex]['page'] as Widget,
      bottomNavigationBar: BottomNavigationBar(
        onTap: _selectPage,
        backgroundColor: Theme.of(context).primaryColor,
        unselectedItemColor: Colors.white,
        selectedItemColor: Colors.lightGreenAccent,
        currentIndex: _selectedPageIndex,
        type: BottomNavigationBarType.fixed,
        //  kiểu bottom bar
        items: [
          BottomNavigationBarItem(
            backgroundColor: Theme.of(context).primaryColor,
            icon: Icon(Icons.category),
            title: Text('Categories'),
          ),
          BottomNavigationBarItem(
            backgroundColor: Theme.of(context).primaryColor,
            icon: Icon(Icons.star),
            title: Text('Favorites'),
          ),
        ],
      ),
    );
  }
}

3, Left navigation bar

Widget build(BuildContext context) {
  return Scaffold(
    appBar: AppBar(
      title: Text(_pages[_selectedPageIndex]['title'] as String),
    ),
    drawer: MainDrawer(), // navigation left
    body: _pages[_selectedPageIndex]['page'] as Widget,

main_drawer:

class MainDrawer extends StatelessWidget {

  Widget buildListTile(String title, IconData icon) {
    return ListTile(
      leading: Icon(icon, size: 26),
      title: Text(
        title,
        style: TextStyle(
          fontFamily: 'RobotoCondensed',
          fontSize: 24,
          fontWeight: FontWeight.bold,
        ),
      ),
      onTap: () {

      },
    );
  }


  @override
  Widget build(BuildContext context) {
    return Drawer(
      child: Column(
        children: [
        Container(
        height: 120,
        width: double.infinity,
        padding: EdgeInsets.all(20),
        alignment: Alignment.centerLeft,
        color: Theme
            .of(context)
            .accentColor,
        child: Text(
          'Cooking Up!',
          style: TextStyle(
            fontWeight: FontWeight.w900,
            fontSize: 30,
            color: Theme
                .of(context)
                .primaryColor,
          ),
        ),
      ),
      SizedBox(
        height: 20,
      ),
      buildListTile('Meals', Icons.restaurant),
      buildListTile('Filters', Icons.settings),
      ],
    ),);
  }
}