I want to put a UIView as a subview to the toppest of all the other subviews. And I want to let this UIView be totally transparent and also let this UIView receive some input events such as slipping over its surface. So I set its alpha to Zero. It is totally transparent after that but the strange thing is it can't receive any input events. And if I tap it, the other UIViews below it would receive the tap event. It seems that the UIView whose alpha=0 disappears or hides. If that's true, I wonder that what's the difference between alpha=0 and hidden=YES?!!! How could it be?!! If alpha=0 and hidden=YES are the same, why do we need property hidden?
If anyone could give me an answer to this question or tell me another way to let a UIView be transparent and receive some input events at the same time, I'll appreciate him/her very much.
Also thank the guys who come in to read my question.
BTW, the UIView can receive events when its alpha value equals or more than 0.02. But I can't let it be 0.02 because of some reasons. I want it to be Zero.