Ios – UIScrollView sending touches to subviews

iosipadiphoneuiscrollviewuiview

Note: I already read some questions about the UIScrollView sending touches to the subviews (this included and although I have up voted, it's not working as I intended anymore).

What I have: I have a UIScrollView with a Custom UIView (let's call it A) inside which covers the entire UIScrollView. I am also allowed to put other custom UIViews inside the A.

On the code I am doing this:

[scrollView setDelaysContentTouches:YES];
scrollView.canCancelContentTouches = NO;

What is happening: At the moment my only issue is that, if I want to move a subview inside A, I have to touch it, wait, and then move it. Exactly as stated here:

Now, the behaviour changes depending on the "length in time" of the
first touch on the UIView. If it's short, then the relative dragging
is managed as it was a scroll for the UIScrollView. If it's long, then
I'm getting the touchesMoved: events inside my UIView.

What I want: The subviews inside A should always receive priority and I shouldn't have to touch and wait. If I touch A and not a subview of it, I want the UIScrollView to receive the touches, like panning and moving around (the contentSize is bigger than the frame).

Edit 1.0

The only reason for me to have this A view inside a generic UIScrollView, is because I want to be able to zoom in/out on the A view. So I am doing the following:

- (UIView *)viewForZoomingInScrollView:(UIScrollView *)scrollView {
    return customView; // this is the A view
}

In the beginning I didn't had the A view inside the UIScrollView and the only thing I did was adding the A as a subView of my UIViewController's root view and everything went well. If there is another way to enable zoom in/out I will gladly accept the answer.

Best Answer

Note: Thank you all for your contributions, specially to Aaron Hayman.

I was able to figure it out by doing the following on the UIScrollView sub-class I had:

-(BOOL)gestureRecognizerShouldBegin:(UIGestureRecognizer *)gestureRecognizer
{
   CGPoint pointOfContact = [gestureRecognizer locationInView:self];

    // The view with a tag of 200 is my A view.
    return (![[self hitTest:pointOfContact withEvent:nil] isEqual:[self viewWithTag:200]]);
}

Related Solutions

Iphone – UIScrollview subviews outside of clipping bounds not receiving touches

This may work:

- (UIView*)hitTest:(CGPoint)point withEvent:(UIEvent*)event {
    UIView* child = nil;
    if ((child = [super hitTest:point withEvent:event]) == self)
        return self.scrollView;         
    return child;
}

But if subview is out of scrollview bounds events were not fired and this function returns self.scrollView.

Ios – Allow UIScrollView and its subviews to both respond to a touch

First, a disclaimer. If you set userInteractionEnabled to NO on the UIScrollView, no touch events will be passed to the subviews. So far as I'm aware, there's no way around that with one exception: intercept touch events on the superview of the UIScrollView, and specifically pass those events to the subviews of UIScrollView. To be honest, though, I don't know why you would want to do this. If you're wanting to disable specific UIScrollView functionality (like...well, scrolling) you can do that easily enough without disabling UserInteraction.

If I understand your question, you need tap events to be processed by the UIScrollView and passed to the subviews? In any case (whatever the gesture is), I think what you're looking for is the protocol method gestureRecognizer:shouldRecognizeSimultaneouslyWithGestureRecognizer: in the protocol UIGestureRecognizerDelegate. In your subviews, whatever gesture recognizers you have, set a delegate (probably whatever class is setting the UIGestureReconginzer in the first place) on the gesture recognizer. Override the above method and return YES. Now, this gesture will be recognized along with any other recognizers that might have 'stolen' the gesture (in your case, a tap). Using this method you can even fine tune your code to only send certain kinds of gestures to the subviews or send the gesture only in certain situations. It gives you a lot of control. Just be sure to read about the method, especially this part:

This method is called when recognition of a gesture by either gestureRecognizer or otherGestureRecognizer would block the other gesture recognizer from recognizing its gesture. Note that returning YES is guaranteed to allow simultaneous recognition; returning NO, on the other hand, is not guaranteed to prevent simultaneous recognition because the other gesture recognizer's delegate may return YES.

Of course, there's a caveat: This only applies to gesture recognizers. So you may still have problems if you're trying to use touchesBegan:, touchesEnded, etc to process the touches. You can, of course, use hitTest: to send raw touch events on to the subviews, but why? Why process the events using those methods in UIView, when you can attach a UIGestureRecognizer to a view and get all of that functionality for free? If you need touches processed in a way that no standard UIGestureRecognizer can provide, subclass UIGestureRecognizer and process the touches there. That way you get all the the functionality of a UIGestureRecognizer along with your own custom touch processing. I really think Apple intended for UIGestureRecognizer to replace most (if not all) of the custom touch processing code that developers use on UIView. It allows for code-reuse and it's a lot easier to deal with when mitigating what code processes what touch event.

Best Answer

Related Solutions

Iphone – UIScrollview subviews outside of clipping bounds not receiving touches

Ios – Allow UIScrollView and its subviews to both respond to a touch

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