Example: Creating space

The following example contains three BlueBox widgets
  and one SizedBox widget that separates the first
  and second BlueBox widgets. The SizedBox widget
  contains a width property equal to 50 logical pixels.

1. Click the Run button.

2. Create more space by adding another
         SizedBox widget (25 logical pixels wide)
         between the second and third BlueBox widgets,
         and run again.

Spacer widget

Similar to SizedBox, the Spacer widget also
can create space between widgets.

Example: Creating more space

The following example separates the first two
  BlueBox widgets using a Spacer widget with
  a flex value of 1.

1. Click the Run button.

2. Add another Spacer widget (also with a flex value of 1)
         between the second and third BlueBox widgets.