Android VideoView.setAlpha is not working (Xoom with 3.0)

currently we're working on a project for Android, doing some Augmented Reality stuff. For this project we need to make a Video played in a VideoView transparent. Since 3.开发者_Python百科0 there should be the method setAlpha() for the VideoView class. But if you change the alpha value by this Method, nothing happens to the view.

Maybe also relevant...the videoView is placed on the top of a GlSurfaceView wich itself is placed over a Surfaceview showing the Camera picture.

Maybe someone got an idea why setAlpha is not working?