DART

sizedbox flutter

SizedBox(
            width: 200.0,
            height: 200.0,
            child: Card(child: Text('Hello World!')),
          ),

sizedbox flutter

   SizedBox(
                  height: 100,
                  width: 100,
                  child: Center(
                    child: CircularProgressIndicator(),
                  ),
                )

sizedbox flutter

// Creates a box with the specified size.
SizedBox.fromSize(
            size: Size.square(200.0),
            child: Card(child: Text('Hello World!')),
          ),