iPhone development - how can I implement transparent overlay view?

I'm now working 开发者_运维百科with view-based application. It's just simple. If I touch the view, the view flips using animation ability of UIView. This is all.

What I want to do after this...is...locating a kind of button in the middle of the main view. BUT!, the button must not be animated while the main view is flipping.

How do I do this?

I dont know this is a correct way or not and i havnt tried this. Just a thought.

Create a UIButton in appdelegate and add that button as subview to the UIWindow. So you can access that button in anyview and so that you can keep that button in the front and change view controllers.