Positions children at the middle of the cross axis. (Middle for Row, Center for Column)

Stretches children across the cross axis.
(Top-to-bottom for Row, left-to-right for Column)

Aligns children by their character baselines.
(Text class only, and requires that the
textBaseline property is set to
TextBaseline.alphabetic.  See the
Text widget section for an example.)

Example: Modifying cross axis alignment

The following example explicitly sets crossAxisAlignment
  to its default value, CrossAxisAlignment.center.

To demonstrate cross axis alignment,
  mainAxisAlignment is set to
 MainAxisAlignment.spaceAround,
  and Row now contains a BiggerBlueBox widget
  that is taller than the BlueBox widgets.

1. Click the Run button.

2. Change CrossAxisAlignment.center to
         CrossAxisAlignment.start, and run again.