ConstrainedBox constructor

ConstrainedBox({Key key, @required BoxConstraints constraints, Widget child })

Creates a widget that imposes additional constraints on its child.

The constraints argument must not be null.

Implementation 

ConstrainedBox({
  Key key,
  @required this.constraints,
  Widget child
}) : assert(constraints != null),
     assert(constraints.debugAssertIsValid()),
     super(key: key, child: child);