content: import 'package:flutter/material.dart';
  import 'package:url_launcher/url_launcher.dart';
  
  class Day8FloatingActionButton extends StatefulWidget {
    Day8FloatingActionButton({Key key}) : super(key: key);
  
    @override
    _Day8FloatingActionButton createState() => _Day8FloatingActionButton();
  }
  
  class _Day8FloatingActionButton extends State<Day8FloatingActionButton> {
    bool _color = true;
  
    @override
    Widget build(BuildContext context) {
      return Scaffold(
        appBar: AppBar(
          title: Text("FloatingActionButton"),
          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/day008_floating_action_btn.dart';
                if (await canLaunch(url)) {
                  await launch(url);
                } else {
                  throw 'Could not launch $url';
                }
              },
            )
          ],
        ),
        floatingActionButton: FloatingActionButton(
          // ? what is FloatingActionButton....
          child: Icon(Icons.add), // ? add the button icon....
          elevation: 10.0, // ! we can give the elevation....
          mini: false, // ! make change here to see the mini effect....
          onPressed: () {
            setState(() {
              _color = !_color; // ! toggle the colors and ui....
            });
          },
        ),
        floatingActionButtonLocation: _color
            ? FloatingActionButtonLocation.centerFloat
            : FloatingActionButtonLocation.centerDocked,
        /**
         * ! [floatingActionButtonLocation] to change the position of ....
         * ! such as : ---
         * * centerFloat, centerDocked, startTop, miniStartTop....
         * * endTop, endFloat, endDocked....
         */
        bottomNavigationBar: BottomAppBar(
          color: _color ? Colors.yellow : Colors.pink,
          child: Container(
            height: 60.0,
          ),
        ),
        body: Container(
          color: _color ? Colors.lightGreen : Colors.white,
        ),
      );
    }
  }
  