content: import 'package:flutter/material.dart';
  import 'package:url_launcher/url_launcher.dart';
  
  class Day40Placeholder extends StatelessWidget {
    const Day40Placeholder({Key key}) : super(key: key);
  
    @override
    Widget build(BuildContext context) {
      return Scaffold(
        body: SafeArea(
          child: Container(
            child: Column(
              children: <Widget>[
                Align(
                  alignment: Alignment.topCenter,
                  /**
                     * ? What is Placeholder....
                     * ! Placeholder is the very simple widget for alocate the place for the upcomming widget....
                     * it have the fallbackHeight, fallbackWidth....
                     * to size the widget....
                     */
                  child: Placeholder(
                    // ! here I am used the Placeholder....
                    fallbackHeight:
                        100, // ! The height to use when the placeholder is in a situation with an unbounded height.
                    fallbackWidth:
                        200, // ! The width to use when the placeholder is in a situation with an unbounded width.
                  ),
                ),
              ],
            ),
          ),
        ),
        appBar: AppBar(
          title: Text("Placeholder"),
          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/day040_placeholder.dart';
                if (await canLaunch(url)) {
                  await launch(url);
                } else {
                  throw 'Could not launch $url';
                }
              },
            )
          ],
        ),
      );
    }
  }
  