Question

In the example project aurioTouch application delegate the code indicates (and I’ve read elsewhere) that the touch event object passed to touchesBegan, touchesMoved, and touchesEnded will be the same object while it is still a single set of user actions, such as touching and moving a finger. When I override UIScrollView and implement these methods, the events that I get back are different objects. What am I missing here?

Answer 1

You are right that the UIEvent is reused when delivering touch events for one gesture. From the docs:

A UIEvent object representing a touch
event is persistent throughout a
multi-touch sequence; UIKit reuses the
same UIEvent instance for every event
delivered to the application. You
should never retain an event object or
any object returned from an event
object. If you need to keep
information from an event around from
one phase to another, you should copy
that information from the UITouch or
UIEvent object.

I presume the difference in behavior for your case results from the special event handling done by UIScrollView. Scroll views delay event delivery because they need to detect a scrolling intent by the user (swipe gestures). So they have to have a way of keeping UIEvents around—probably copying them to make sure they retain their original state. This might be the reason you see different objects.

Note that all of the above is only guessing.