FractionallySizedBox constructor

const FractionallySizedBox({Key key, AlignmentGeometry alignment: Alignment.center, double widthFactor, double heightFactor, Widget child })

Creates a widget that sizes its child to a fraction of the total available space.

If non-null, the widthFactor and heightFactor arguments must be non-negative.

Implementation 

const FractionallySizedBox({
  Key key,
  this.alignment = Alignment.center,
  this.widthFactor,
  this.heightFactor,
  Widget child,
}) : assert(alignment != null),
     assert(widthFactor == null || widthFactor >= 0.0),
     assert(heightFactor == null || heightFactor >= 0.0),
     super(key: key, child: child);