Single Tapping not being detected on dynamically created uibuttons

Question

It was necessary to create a subclass of UIButton, lets call it subButton. These subButtons are instantiated one by one and dynamically added to an UIScrollView object.

Unfortunately the subButtons aren't reacting as expected. After scrolling away from the first dynamic generated subButtons and then returning back to them. They loose their reactivity to single tapping. I can not explain this behaviour. Can somebody explain why its behaving this way?

Many thanks.

Source code

self.subButton = [[SubButton alloc]initWithFrame:CGRectMake(69.5, y, 201, 114)];
[self.subButton setBackgroundColor:[UIColor blueColor]];
self.subButton.imageData = imageData;
self.subButton.videoPath = videoPath;
self.subButton.vidIndex = _indexVideo +1;
[self.subButton drawVidPreview];
[self.subButton setTag:(_indexVideo +1)];
[self.subButton addTarget:self action:@selector(handleSingleTap:) forControlEvents:UIControlEventTouchUpInside];
[self.videoScroll addSubview:self.subButton];
[_videoPreviews addObject:self.subButton];

The subButton method drawVidPreview adds some subviews to itself.

Answer 1

Please make sure you are not adding the same UIGestureRecognizer instance to all of the UIButtons, instead for each UIButton you need to add a separate instance, however all gesture instance can point to the same target.

Answer 2

At last, i could solve the problem. The reason why the first subButtons did not respond to single tapping with UIControlEventTouchDown is because the uiScrollview content offset was set to a negative y value. This first of all was not necessary and was done out of pure laziness. I corrected it by giving it a positive value.

So my conclusion is, if you do not set the content offset or content size of the scrollView correctly, some dynamically added buttons to the scrollView might not respond to tapping appropriately. This is even the case if all Buttons are placed completely on a uiScrollview object.

This I could confirm by playing around with the content size of the uiScrollview instance too. I changed size of the y value of uiScrollviews instance just by few points and then some of the last buttons did not respond to tapping anymore.

Just by increasing the content size of the y value again, made the buttons responsive again.

Answer 3

Do the buttons not respond at all, or just not to single-tap? That might help us help you.

If they don't respond at all, I would check your view hierarchy to make sure no other view (perhaps invisible) are sitting above your buttons. Or, perhaps are the buttons not being added to the parent view you think?