Question

In iOS 4 I believed -touchesBegan:withEvent:, -touchesMoved:withEvent:, -touchesEnded:withEvent:, -touchesCancelled:withEvent: were the only methods available to implement in a view to handle touches.

But now when I override these methods like this:

- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
    // not calling super. Doing nothing.
}

in a UIScrollView subclass, it still scrolls. How did they do it?

Answer 1

UIScrollView uses a UIPanGestureRecognizer to scroll. UIKit sends events to gesture recognizers through a private mechanism, separate from touchesBegan:withEvent: and related methods.