CABasicAnimation not started when adding animation to a layer that is not visible

Question

Hi Stackoverflow,

I'm trying to create a little glow-animation with Core Animation. Animation works fine so far. Problem is, the animation is used in a table cell. When the animation is added to a layer that is currently in a cell that is not yet visible (without scrolling), the animation is not started somehow? Seems as if CoreAnimation won't animate layers that are not currently visible?

My code is:

CABasicAnimation *animation = [CABasicAnimation animationWithKeyPath:@"opacity"];
[animation setFromValue:[NSNumber numberWithFloat:0.0]];
[animation setToValue:[NSNumber numberWithFloat:1.0]];
[animation setDuration:self.currentBlinkFrequency];
[animation setTimingFunction:[CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionLinear]];
[animation setAutoreverses:YES];
[animation setRepeatCount:HUGE_VALF];
[[self.signalImage layer] addAnimation:animation forKey:@"opacity"];    

Answer 1

Okay found a workaround. I used UIView animation methods instead. Because my animation speed can be changed/switched off during animation I needed to use the following code to avoid kicking of multiple animations on the same view.

This code triggeres the animation :

if (self.currentBlinkFrequency == 0) {
    self.shouldContinueBlinking = FALSE;
    self.animationIsRunning = FALSE;
} else {
    self.shouldContinueBlinking = TRUE;
    if (self.animationIsRunning == FALSE) {
        self.animationIsRunning = TRUE;
        [self blinkAnimation:@"blink" finished:YES target:self.signalImage];            
    }
}

The invoked anomation code for the "blinkAnimation"-method is borrowed from another post in stackoverflow here

- (void)blinkAnimation:(NSString *)animationId finished:(BOOL)finished target:(UIView *)target
{
    if (self.shouldContinueBlinking) {
        [UIView beginAnimations:animationId context:target];
        [UIView setAnimationDuration:self.currentBlinkFrequency];
        [UIView setAnimationDelegate:self];
        [UIView setAnimationDidStopSelector:@selector(blinkAnimation:finished:target:)];
        if ([target alpha] == 1.0f)
            [target setAlpha:0.0f];
        else
            [target setAlpha:1.0f];
        [UIView commitAnimations];
    }
}