Propagate dragging touch to UIScrollView superview

Question

I have been looking to all the other similar topics here, using UIGestureRecognizers, using hitTest:withEvent, pointInside:withEvent: etc. but nothing seems to be ok for what I need to achieve.

Basically I have a main view (self.view of a common UIViewController) and a small rectangular UIScrollView attached onto it at the bottom: the scrollView is filled with some UIImageViews and the user can scroll it as usual.

But the user should also be able to drag one UIImageView (or a copy of it) from the UIScrollView to the main view, and, this is what I am finding really difficult, with the SAME dragging gesture, hence I need a way to:

1) Distinguish between normal horizontal scrolling gesture, which should be handled by the UIScrollView the usual way and a dragging gesture over the image view.

2) Once identified a dragging gesture, should propagate the touch to the superview, which will host a copy of the UIImageView and WITH the SAME dragging gesture continue the dragging over the main view even out of the bounds of the UIScrollView.

Please note that I know that if the UIScrollView has userInteractionEnabled = NO the touch is propagated to the subviews, but 1) I want to propagate it to the superview not the subviews, 2) the userInteractionEnabled property apparently becomes active only once the initial gesture is terminated, while I need to use a single dragging gesture.

Thank you very much for any help.

Answer 1

So, so far I have ended up implementing the touchesShouldBegin:withEvent:inContentView: method of my UIScrollView subclass but with delayContentTouches set to YES (default) instead of NO as @nhahtdh was suggesting.

Strangely enough even only implementing the method was sufficient for my subviews to intercept the dragging, and still my scrollview is scrolling properly, while with delayContentTouches set to NO I was not able to scroll it as all the subviews were starting to move around.

Really the credit for this is @nhahtdh, so man, if you post an answer I will accept it, thank you very much for your help.