How can an underlying view know if it's rectangle got touched, no matter if directly or indirectly?

Question

This is for learning:

I have an UIView which is transparent and covers almost the whole screen. I left 50 pixels at the top. It is a child of the View Controller's view.

Underneeth the UIView there's MyView that inherits from UIView, which matches the screen size. And inside this MyView class, I ask for a touch on it very simple with this:

• (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event { UITouch *touch = [touches anyObject];

  if ([touch view] == self) { NSLog(@"MyView touched"); } }

Now the funny thing is, of course, that if the user touches on the transparent UIView which covers that MyView, I don't get "MyView touched" in the console. But when the user touches the little uncovered area of MyView at the top of the screen, then the touch arrives there.

That's logical to me, because I ask for [touch view] == self. But what if I wanted to know that the rectangular area of that MyView got touched (no matter if indirect or direct)?

Is there a way to catch any touch that appears on the screen/window and then just check if it matches the rectangular area of the view?

Answer 1

You should study the iPhone Application Programming Guide's section on Touch Events for the background you're looking for. The concept you want to master is the Responder Chain, so also look through the reference on UIResponder to understand what it's doing. You can definitely do everything you're talking about, and the full discussion is in the link above.