Container is a widget that combines common painting, positioning, and sizing widgets. Flutter Container widget is used frequently in a Flutter app’s screen.

Container( padding: const EdgeInsets.all(16.0), color: Colors.blue, width: 100.0, height: 100.0, child: Text('100.0'), )
Make container fill the whole screen
Container( padding: const EdgeInsets.all(16.0), color: Colors.blue, width: double.infinity, height: double.infinity, child: Text('infinity'), )
Container( padding: const EdgeInsets.all(16.0), color: Colors.blue, width: MediaQuery.of(context).size.width, height: MediaQuery.of(context).size.height, child: Text('media size'), )
Container with border and radius

Container( padding: const EdgeInsets.all(8.0), width: 200.0, height: 200.0, decoration: BoxDecoration( border: Border.all(color: Colors.blueAccent), borderRadius: BorderRadius.all(Radius.circular(6.0)), ), child: Text("Border"), )