UIScrollView touch events delivering

split · November 2009

I have quite complex problem with UIScrollView which is different from all problems resolved here. Anyway I think what can help me if someone explains me this:

I made up a subclass of UIScrollView and overrode all touch based methods (touchesBegan, touchesMoved...) I filled it only with NSLog, with no [super ...] calling. What I don't understand is that this subclass of UIScrollView still works. I mean it still scrolls. How is this possible. Is there any other place or technique how can object recieve touch events? Or is there another view below actual scroll view (which is still part of UIScrollView) which overrides the hitTest?

I need to track all the scroll view touch events and don't interact with normal scrolling behavior of scroll view. Is there a way to do this?

I'm really not in mood of creating my own scroll view from beginning :)

fiftysixty · November 2009

Since OS 3.0 (I think) touchesBegin, -Moved etc. have been deprecated in UIScrollView. It's a bummer, though it was apparently done to avoid certain problems. Currently, the only way to customize touch handling in a UIScrollView is with touchesShouldBegin:withEvent:inContentView which is not much to be honest.

After reading through iPhone Dev Center: iPhone Application Programming Guide: Event Handling I don't think there is a good way for you to do what you want, the only real option being subclassing UIWindow and overriding the sendEvent: method, but calling the superclass implementation so that the touches get sent properly.

split · November 2009

Thanks for reply.

Unfortunately I know about everything what you wrote. I read "Event Handling" chapter about 20 times :) I allready did override sendEvent: method (but in UIApplication) and it may help me but this solution is really not very nice. It is also strange that the view of events when touches began is set to my custom scroll view, but after moving finger a little bit it changes to NULL.

Anyway there is probably something what is not really documented at all. Originally I thought sendEvent looks for first responder and calls touchesBegin, touchesCancelled ... methods. This is probably not the whole truth.

Solution: I will create my own scroll view :) Thank you apple :)

fiftysixty · November 2009

From what I understand, sendEvent: performs hitTest: on the view hierarchy to find the view that should handle the touch, and then the view either handles it or passes it to its nextResponder (usually the view controller) for handling, and this goes on until a view or view controller handles the touches, or until the UIApplication handles or discards them.

After the changes in 3.0, I had to create my own scroll view too, but it's very basic: no scroll bars, no kinetic scrolling, but still it scrolls and zooms in and out, and that's what matters to me :)

split · January 2010

After quite a long period of time I found solution to all my problems with UIScrollView.

To be able to track position of touches and also don't interact with UIScrollView I ended up with subclassing application key window (UIWindow) and overriding sendEvent method.

Here is a code:

- (void)sendEvent:(UIEvent *)event {
	[super sendEvent:event];
	
	// only if it is a touch event type and we have observer
	if ((touchesObserver) && (event.type == UIEventTypeTouches)) {
	
		// empty sets
		[beganTouches removeAllObjects];
		[cancelTouches removeAllObjects];
		[endTouches removeAllObjects];
		[moveTouches removeAllObjects];
		
		// fill in sets
		for (UITouch * touch in [event allTouches]) {
			if (touch.phase == UITouchPhaseBegan) [beganTouches addObject:touch];
			else if (touch.phase == UITouchPhaseCancelled) [cancelTouches addObject:touch];
			else if (touch.phase == UITouchPhaseMoved) [moveTouches addObject:touch];
			else if (touch.phase == UITouchPhaseEnded) [endTouches addObject:touch];
		}
		
		// call methods
		if ([beganTouches count] > 0) [touchesObserver touchesBegan:beganTouches withEvent:event];
		if ([cancelTouches count] > 0) [touchesObserver touchesCancelled:cancelTouches withEvent:event];
		if ([moveTouches count] > 0) [touchesObserver touchesMoved:moveTouches withEvent:event];
		if ([endTouches count] > 0) [touchesObserver touchesEnded:endTouches withEvent:event];		
	}
}

- touchesBegan, touchesCancelled ... are NSMutableSet objects
- touchesObserver is any UIResponder object and it recieves all touches which occure in application.

This is much more powerfull than I needed, but it helps me do what I need. Hopefully it will help someone else too :)

LaMarmotte · April 2010

split;158475 said:
After quite a long period of time I found solution to all my problems with UIScrollView.

To be able to track position of touches and also don't interact with UIScrollView I ended up with subclassing application key window (UIWindow) and overriding sendEvent method.

Here is a code:
- (void)sendEvent:(UIEvent *)event {
	[super sendEvent:event];
	
	// only if it is a touch event type and we have observer
	if ((touchesObserver) && (event.type == UIEventTypeTouches)) {
	
		// empty sets
		[beganTouches removeAllObjects];
		[cancelTouches removeAllObjects];
		[endTouches removeAllObjects];
		[moveTouches removeAllObjects];
		
		// fill in sets
		for (UITouch * touch in [event allTouches]) {
			if (touch.phase == UITouchPhaseBegan) [beganTouches addObject:touch];
			else if (touch.phase == UITouchPhaseCancelled) [cancelTouches addObject:touch];
			else if (touch.phase == UITouchPhaseMoved) [moveTouches addObject:touch];
			else if (touch.phase == UITouchPhaseEnded) [endTouches addObject:touch];
		}
		
		// call methods
		if ([beganTouches count] > 0) [touchesObserver touchesBegan:beganTouches withEvent:event];
		if ([cancelTouches count] > 0) [touchesObserver touchesCancelled:cancelTouches withEvent:event];
		if ([moveTouches count] > 0) [touchesObserver touchesMoved:moveTouches withEvent:event];
		if ([endTouches count] > 0) [touchesObserver touchesEnded:endTouches withEvent:event];		
	}
}
- touchesBegan, touchesCancelled ... are NSMutableSet objects
- touchesObserver is any UIResponder object and it recieves all touches which occure in application.

This is much more powerfull than I needed, but it helps me do what I need. Hopefully it will help someone else too :)

Hello, could you give us more information about this? I tried to do teh same but without success.

Thanks

split · April 2010

What's the problem you have? Did you subclass main application window? There is no more information about this. I think I've described it completly.

rocotilos · April 2010

What I did is different. Just sharing.

I have a UIImageView in UIScrollView. So users be able to pan/zoom in as normal. Then when I want to do something on the UIImageView, i just remove the UIImageView from the UIScrollview and then the touches will be effective.

MCG · October 2010

split;158475 said:
After quite a long period of time I found solution to all my problems with UIScrollView.

To be able to track position of touches and also don't interact with UIScrollView I ended up with subclassing application key window (UIWindow) and overriding sendEvent method.

Here is a code:
- (void)sendEvent:(UIEvent *)event {
	[super sendEvent:event];
	
	// only if it is a touch event type and we have observer
	if ((touchesObserver) && (event.type == UIEventTypeTouches)) {
	
		// empty sets
		[beganTouches removeAllObjects];
		[cancelTouches removeAllObjects];
		[endTouches removeAllObjects];
		[moveTouches removeAllObjects];
		
		// fill in sets
		for (UITouch * touch in [event allTouches]) {
			if (touch.phase == UITouchPhaseBegan) [beganTouches addObject:touch];
			else if (touch.phase == UITouchPhaseCancelled) [cancelTouches addObject:touch];
			else if (touch.phase == UITouchPhaseMoved) [moveTouches addObject:touch];
			else if (touch.phase == UITouchPhaseEnded) [endTouches addObject:touch];
		}
		
		// call methods
		if ([beganTouches count] > 0) [touchesObserver touchesBegan:beganTouches withEvent:event];
		if ([cancelTouches count] > 0) [touchesObserver touchesCancelled:cancelTouches withEvent:event];
		if ([moveTouches count] > 0) [touchesObserver touchesMoved:moveTouches withEvent:event];
		if ([endTouches count] > 0) [touchesObserver touchesEnded:endTouches withEvent:event];		
	}
}
- touchesBegan, touchesCancelled ... are NSMutableSet objects
- touchesObserver is any UIResponder object and it recieves all touches which occure in application.

This is much more powerfull than I needed, but it helps me do what I need. Hopefully it will help someone else too :)

Thanks,it helps me a lot.:p

mejim707 · May 2012

I'm looking to track touches in a scroll view as well. In my case I want to be able to have a UIView move with the scroll view as you scroll it. I want the UIView from outside the UIScrollView to move tracking the position of a button within the UIScrollView. So, if you tap the button in the scroll view the outside UIView appears. Then it you scroll the scrollview the UIView moved with the button you just tapped. I can't seem to track touches within the Scroll view even though I've subclassed it. Is there anything I can do to get this behavior? As an FYI, we have gestures and other scroll views configured in the view and we don't want to loose these. It seems that the above code would take control over all touches within the view thus breaking our gestures and other scroll views.

Thanks

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UIScrollView touch events delivering

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