Make circular joystick

Question

How do I make a joystick like the one in i dig it, using UIImageView's that the smaller one can be used to move around, I just really would like to know how I would get the smaller UIImageView to stay inside the larger one, I just don't know how I would do this because they are both circular. I have an Image below:

Answer 1

There's some code for a Virtual Joystick in the cocos2d discussion group that you may find useful: http://groups.google.com/group/cocos2d-iphone-discuss/browse_thread/thread/7b34fc0d215f68bf?pli=1

Also, of some interest with regards to implmentation: http://forums.toucharcade.com/showthread.php?t=44277