title: iPhone: Synchronize animations on two different layers
body: <p>I need to synchronize a path animation on two different layers (one is used as a mask for another layer, the other shows a graphical element that follows the path, i.e. draws the mask). If I just set them up identically, they never quite do the same thing. Currently, I am using a CAKeyframeAnimation with a path (for the graphical element) and a CABasicAnimation, where I animate "strokeEnd" of the same path from 0.0 to 1.0 (for the mask).</p>
  
  <p>I guess an animation group does not work here, since that would mean I apply the group to the mask layer, which would hide the graphical element.</p>