DragEndDetails constructor

DragEndDetails({Velocity velocity: Velocity.zero, double primaryVelocity })

Creates details for a GestureDragEndCallback.

The velocity argument must not be null.

Implementation 

DragEndDetails({
  this.velocity = Velocity.zero,
  this.primaryVelocity,
}) : assert(velocity != null),
     assert(primaryVelocity == null
         || primaryVelocity == velocity.pixelsPerSecond.dx
         || primaryVelocity == velocity.pixelsPerSecond.dy);