如何使一个层列表项具有动画效果

I have a layer list object, it contain two images, one is background, and the other is a rotation disk image which will be raotated at the top of the background image. i.e. I use this layer-list as a linearlayout background, and I only want to animate "disk_bg" item of the layer-list;I have a layer list object, it contain two imag