content: import 'package:flutter/material.dart';
  import 'package:url_launcher/url_launcher.dart';
  
  class Day35Spacer extends StatelessWidget {
    const Day35Spacer({Key key}) : super(key: key);
  
    @override
    Widget build(BuildContext context) {
      return Scaffold(
        body: SafeArea(
          child: Center(
            child: Container(
              width: MediaQuery.of(context).size.width * 0.5,
              height: MediaQuery.of(context).size.height * 0.5,
              decoration: BoxDecoration(
                border: Border.all(color: Colors.black, width: 2),
              ),
              child: Column(
                children: <Widget>[
                  Container(
                    width: double.infinity,
                    height: 20,
                    color: Colors.red[200],
                  ),
                  Spacer(), // ? What is Spacer....
                  /**
                   * ! Spacer is the simple filler between the Ui Widgets....
                   * ! we can give the [flex] value to fill between the spaces....
                   */
                  Container(
                    width: double.infinity,
                    height: 20,
                    color: Colors.yellow[200],
                  ),
                  Spacer(
                    flex: 2,
                  ),
                  /**
                   * ! here we use the flex value as 2...
                   * ! so it will automatically take the ratio 1:2 space between the Conatiners....
                   */
                  Container(
                    width: double.infinity,
                    height: 20,
                    color: Colors.green[200],
                  ),
                ],
              ),
            ),
          ),
        ),
        appBar: AppBar(
          title: Text("Spacer"),
          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/day035_spacer.dart';
                if (await canLaunch(url)) {
                  await launch(url);
                } else {
                  throw 'Could not launch $url';
                }
              },
            )
          ],
        ),
      );
    }
  }
  