UIButton flashing animation

Question

I was wondering if it was possible to apply a flashing animation to a UIButton. I have searched but only found the code for a pulse animation which changes the size of my UIButton continuously. I instead was thinking about some kind of flashing animation to alert the user he has to press the button. The only approach to the problem I can think of is by changing the alpha constantly using:

[self setAlpha:0.5]; 

...but it won't be as visible as a flashing button.

Answer 1

Perhaps not the best way, and doesn't really allow you to stop the flashing... but this is simple, works, and does not hinder user interaction:

- (void)viewDidLoad
{
    [self flashOn:myButton];
}

- (void)flashOff:(UIView *)v
{
    [UIView animateWithDuration:.05 delay:0 options:UIViewAnimationOptionAllowUserInteraction animations:^ {
        v.alpha = .01;  //don't animate alpha to 0, otherwise you won't be able to interact with it
    } completion:^(BOOL finished) {
        [self flashOn:v];
    }];
}

- (void)flashOn:(UIView *)v
{
    [UIView animateWithDuration:.05 delay:0 options:UIViewAnimationOptionAllowUserInteraction animations:^ {
        v.alpha = 1;
    } completion:^(BOOL finished) {
        [self flashOff:v];
    }];
}

Answer 2

Reading all the answers so far I found following solution. It repeats a number of times and does the job for me.

CGFloat oldAlpha = v.alpha;
CGFloat minAlpha = 0.2;
enum UIViewAnimationOptions options = UIViewAnimationOptionAllowUserInteraction | UIViewAnimationOptionAutoreverse | UIViewAnimationOptionCurveEaseInOut;

[UIView animateWithDuration:.3 delay:0.3 options:options animations:^{
    [UIView setAnimationRepeatCount:4];
    v.alpha = minAlpha;
}
completion:^(BOOL finished) {
    v.alpha = oldAlpha;
}];