UIButton at bottom of screen only intermittently highlights

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?

The buttons sometimes don't highlight when the user taps on them? And what do you mean by "Control Center's" gesture recognizer. Do you mean the buttons' built-in gesture recognizers? — bilobatum, Sep 30 '13 at 02:43
I've edited my question. When the user taps a button at the bottom of the screen it only intermittently gets highlighted. This is due to the swipe gesture reserved for bringing up Control Center blocking the highlighting. — Aaron Shekey, Sep 30 '13 at 03:22
have you tried setting UIControlStateSelected with button.selected = YES? — Farhan Hafeez, Sep 30 '13 at 05:09
@FarhanHafeez, yes I've tried using UIControlStateSelected. No dice. The problem is UIButton state related. Events fire but states do not change. Pretty sure I need to build a component that LOOKS and FUNCTIONS like a button in order to get around it. — Aaron Shekey, Sep 30 '13 at 15:17

score 5 · Accepted Answer · answered Dec 26 '13 at 06:13

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
}

score 3 · Answer 2 · edited Apr 16 '14 at 07:23

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!

This is technically a solution, yes, but it requires changing the fundamental user experience by hiding the status bar AND disabling the back gesture. My app wouldn't be an appropriate place to hide the status bar or disable the back gesture. — Aaron Shekey, May 05 '14 at 19:08

score 2 · Answer 3 · edited May 23 '17 at 12:02

2

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

edited May 23 '17 at 12:02

Community

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answered May 21 '14 at 15:10

Quxflux

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Above mentioned solution "setting highlighted state image" seems good. But, the solution provided in the thread mentioned in this comment seems perfect. – Satish Jul 31 '14 at 06:08

score 0 · Answer 4 · answered Feb 11 '16 at 12:49

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

UIButton at bottom of screen only intermittently highlights

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