content: import 'package:flutter/material.dart';
  import 'package:url_launcher/url_launcher.dart';
  
  class Day66DefaultTabControllerAndTabBar extends StatefulWidget {
    Day66DefaultTabControllerAndTabBar({Key key}) : super(key: key);
  
    @override
    _Day66DefaultTabControllerAndTabBarState createState() =>
        _Day66DefaultTabControllerAndTabBarState();
  }
  
  class _Day66DefaultTabControllerAndTabBarState
      extends State<Day66DefaultTabControllerAndTabBar> {
    @override
    Widget build(BuildContext context) {
      // ? What is DefaultTabController, TabBar & TabBarView....
      /**
       * ! To impelment the Tabs in the Flutter we need to maintain and understand the there important Widget....
       * * 1 - DefaultTabController to control the UiChange....
       * * 2 - TabBar to display the Tabs in [appBar]....
       * * 3 - TabBarView to display the current Page corresponding to Tabs....
       */
      return DefaultTabController(
        // ! here we added the [DefaultTabController]....
        length: 3, // ! [length] denote the total tabs....
        initialIndex: 1, // ! here we initialize the stating tab....
        child: Scaffold(
          appBar: AppBar(
            bottom: TabBar(
              tabs: [
                // ! here we added the [TabBar] at the bottom of the [appBar]....
                // ! and added the tabs one by one....
                Tab(
                  child: Text("Left"),
                ),
                Tab(
                  child: Text("Mid"),
                ),
                Tab(
                  child: Text("Right"),
                ),
              ],
            ),
            title: Text('DefaultTabController, \nTabBar & TabBarView'),
            actions: <Widget>[
              IconButton(
                icon: Icon(Icons.help),
                onPressed: () async {
                  const url =
                      'https://github.com/sanjaysanju618/100-Days-Of-Flutter-Widgets/' +
                          'blob/master/hundred_days_of_flutter_widget/' +
                          'lib/day066_default_tab_controller_and_tab_bar.dart';
                  if (await canLaunch(url)) {
                    await launch(url);
                  } else {
                    throw 'Could not launch $url';
                  }
                },
              )
            ],
          ),
          body: SafeArea(
            child: TabBarView(
              // ! here we added the [TabBarView]....
              children: [
                // ! to the [children] of the TabBarView we added the actual tabs views....
                Center(
                  child: Text(
                    "This is Left Side",
                    style: TextStyle(fontSize: 30, color: Colors.pink),
                  ),
                ),
                Center(
                  child: Text(
                    "This is Middle",
                    style: TextStyle(
                      fontSize: 30,
                      color: Colors.purple,
                    ),
                  ),
                ),
                Center(
                  child: Text(
                    "This is Right Side",
                    style: TextStyle(fontSize: 30, color: Colors.deepOrange),
                  ),
                ),
              ],
            ),
          ),
        ),
      );
    }
  }
  