UIButton at bottom of screen only intermittently highlights - ios

Question

I have a few UIButtons at the bottom of my app's main view. These buttons intermittently don't highlight when a user taps them but their target methods always get called. I've discovered it's Control Center's gesture recognizer getting in the way of UIButton's highlighting. If I move the containing view up toward the middle of the screen everything functions as designed.
The issue is reported here https://devforums.apple.com/message/865922
As a workaround I've tried setting the highlighted state by hand with the target method. This seems to have the same effect of allowing the UIButton to highlight normally.
Any ideas how to work around this without redesigning these controls to appear elsewhere in the app?
Perhaps I use a standard view and add all the methods for touch interaction by hand? How would I do that? Is it even worth exploring?

Answer 1

I've found a pretty simple workaround for this. Using standard properties like .highlighted = YES and .selected = YES doesn't seem to work within that bottom band. Instead of setting the highlighted state, I just set the background image of the button to the highlighted state with an unperceived delay BEFORE we call the final method.
[self.stopRecordingButton setImage:[UIImage imageNamed:#"stopRecordingButton"] forState:UIControlStateNormal];
[self.stopRecordingButton setImage:[UIImage imageNamed:#"stopRecordingButton-highlighted"] forState:UIControlStateHighlighted];
[self.stopRecordingButton addTarget:self action:#selector(stopRecordingDelay) forControlEvents:UIControlEventTouchUpInside];
-(void)stopRecordingDelay
{
[self.stopRecordingButton setImage:[UIImage imageNamed:#"stopRecordingButton-highlighted"] forState:UIControlStateNormal];
[self performSelector:#selector(stopRecording) withObject:nil afterDelay:0.025f];
}
- (void)stopRecording
{
[self.stopRecordingButton setImage:[UIImage imageNamed:#"stopRecordingButton"] forState:UIControlStateNormal];
//Do real stuff
}

Answer 2

I recently ran into the same problem and search everywhere for an answer. This is what worked for me. It was a combination of two things, the UINavigationController back swipe gesture and the iOS 7 control center gesture (up swipe from bottom of the screen).
Disable the back swipe gesture if on a UINavigationController:
in viewDidLoad:
if ([self.navigationController respondsToSelector:#selector(interactivePopGestureRecognizer)]) {
self.navigationController.interactivePopGestureRecognizer.enabled = NO;
}
Set the control center gesture to only show an up arrow instead of showing the control center first. You can do this by overriding the following UIViewController method:
- (BOOL)prefersStatusBarHidden {
return YES;
}
Hope this helps!

Answer 3

I've posted a fix for this issue that brings the highlight back described in this question. The highlight is fixed by subclassing UIButton and overriding pointInside: to catch touch events

Answer 4

If you have a button that's covering the whole bottom of the screen you may run into an issue where only the left part has this delay.
In order to normalize feedback time for the whole button one might use the following solution
(an improved version of Aaron Shekey's):
NSDate *touchDownTime;
- (void)touchDown
{
self.alpha = 0.7;
touchDownTime = [NSDate date];
}
- (void)touchUpInside
{
// basically at least 80ms feedback is guaranteed this way
// note: timeIntervalSinceNow returns negative
NSTimeInterval feedbackTimeLeftToShow =
MAX(0.08 + [touchDownTime timeIntervalSinceNow], 0.001);
[self performSelector:#selector(touchUpInsideAfterFeedback)
withObject:nil
afterDelay:feedbackTimeLeftToShow];
}
- (void)touchUpInsideAfterFeedback
{
self.alpha = 1;
}
note: performSelector may do well with negative delay values, but better be safe than sorry