UIButton is unclickable after change in container height - ios

Question

An UIButton is contained inside a UIScrollView. I have this setup in a xib. I use a NSLayoutConstraint to change the height of the scrollview. After I click the button, the scrollview changes height, but then UIButton becomes unclickable.
Here is the code:
- (IBAction)TagPressed:(UIButton *)sender {
if (self.height.constant == 200) {
self.height.constant = 88;
}else
self.height.constant = 200;
[self.view setNeedsUpdateConstraints];
[UIView animateWithDuration:0.5f animations:^{
[self.view layoutIfNeeded];
}];
DRect(_scrollView.frame)
DRect(self.view.frame)
DRect(sender.frame)
NSLog(sender.selected ? #"Selected" : #"Not Selected");
}
Drect is a nslog for frames. So the Console out is:
2013-04-08 17:04:19.264 TouchSelectApp[93618:c07] CGRect ( 20.000000, -112.000000, 62.000000, 200.000000)
2013-04-08 17:04:19.266 TouchSelectApp[93618:c07] CGRect ( 0.000000, 300.000000, 320.000000, 88.000000)
2013-04-08 17:04:19.266 TouchSelectApp[93618:c07] CGRect ( 7.000000, 78.500000, 48.000000, 44.000000)
Output from (lldb) po [[UIApp keyWindow] recursiveDescription]
I had to add a an extra button to create a debugging stop. The button I care about is inside SelectableTag.
$0 = 0x0887e0e0 <UIWindow: 0x7197a90; frame = (0 0; 320 568); autoresize = W+H; layer = <UIWindowLayer: 0x7199620>>
| <UIView: 0x719ed20; frame = (0 20; 320 548); autoresize = W+H; layer = <CALayer: 0x719edd0>>
| | <UIRoundedRectButton: 0x719b9d0; frame = (51 464; 73 44); opaque = NO; autoresize = TM+BM; layer = <CALayer: 0x719baf0>>
| | | <UIGroupTableViewCellBackground: 0x719c2a0; frame = (0 0; 73 44); userInteractionEnabled = NO; layer = <CALayer: 0x719c370>>
| | | <UIImageView: 0x719da50; frame = (1 1; 71 43); opaque = NO; userInteractionEnabled = NO; layer = <CALayer: 0x719dd20>>
| | | <UIButtonLabel: 0x719d0f0; frame = (12 12; 49 19); text = 'Button'; clipsToBounds = YES; opaque = NO; userInteractionEnabled = NO; layer = <CALayer: 0x719d1e0>>
| | <UIView: 0x71a1160; frame = (0 300; 320 88); autoresize = RM+BM; layer = <CALayer: 0x71a11c0>>
| | | <SelectableTag: 0x719fcc0; baseClass = UIScrollView; frame = (20 -112; 62 200); clipsToBounds = YES; autoresize = W+H; gestureRecognizers = <NSArray: 0x71a04e0>; layer = <CALayer: 0x719fef0>; contentOffset: {0, 0}>
| | | | <UIImageView: 0x71a0c20; frame = (55 193; 7 7); alpha = 0; opaque = NO; autoresize = TM; userInteractionEnabled = NO; layer = <CALayer: 0x71a0cc0>>
| | | | <UIImageView: 0x71a0dd0; frame = (55 62; 7 7); alpha = 0; opaque = NO; autoresize = LM; userInteractionEnabled = NO; layer = <CALayer: 0x71a0e70>>
| | | | <UIRoundedRectButton: 0x719ddd0; frame = (-1 7; 64 44); opaque = NO; layer = <CALayer: 0x719b630>>
| | | | | <UIGroupTableViewCellBackground: 0x719d630; frame = (0 0; 64 44); userInteractionEnabled = NO; layer = <CALayer: 0x719b690>>
| | | | | <UIImageView: 0x719dea0; frame = (1 1; 62 43); opaque = NO; userInteractionEnabled = NO; layer = <CALayer: 0x719d990>>
| | | | | <UIButtonLabel: 0x71a1630; frame = (12 12; 40 19); text = 'Test1'; clipsToBounds = YES; opaque = NO; userInteractionEnabled = NO; layer = <CALayer: 0x71a1e50>>
(lldb)

Answer 1

From the documentation of hitTest:withEvent: in the UIView Class Reference:
Points that lie outside the receiver’s bounds are never reported as hits, even if they actually lie within one of the receiver’s subviews. This can occur if the current view’s clipsToBounds property is set to NO and the affected subview extends beyond the view’s bounds.
The parent of your scroll view is the view with address 0x71a1160. Notice that the scroll view's frame.origin.y is -112. So the top 112 points of the scroll view are outside of its parent's bounds. That part of the scroll view will never receive touches. Your Test1 button is entirely in that part of the scroll view.

Answer 2

I have noticed this behavior too with UIButtons. After changing the frame of the parent view, if you add the button again it will work.