CABasicAnimation is not working when the method is called from the viewDidLoad

Question

I have an imageView added to a view that's presented as a modalViewController, with style horizontal flip. I have added the following code for animating the imageView.

- (void)animateTheImageview:(UIImageView*) imageViewToAnimate{
    
    CABasicAnimation *fadeAnimation;
    fadeAnimation = [CABasicAnimation animationWithKeyPath:@"opacity"];
    fadeAnimation.duration = 1.5;
    fadeAnimation.repeatCount = INFINITY;
    fadeAnimation.autoreverses = NO;
    fadeAnimation.fromValue = [NSNumber numberWithFloat:1.0];
    fadeAnimation.toValue = [NSNumber numberWithFloat:0.5];
    fadeAnimation.removedOnCompletion = YES;
    fadeAnimation.fillMode = kCAFillModeForwards;
    [imageViewToAnimate.layer addAnimation:fadeAnimation forKey:@"animateOpacity"]; 
}


- (void)switchOnorOff
 {
    
    if (onOffSwitch.on)
    {
        
        self.lightImage.image = [UIImage imageNamed:@"CFLGlow.jpg"];
        [self animateTheImageview:self.lightImage];
    }
    else
    {
        
        self.lightImage.image = [UIImage imageNamed:@"CFL-BULB.jpg"];
        [self.lightImage.layer removeAllAnimations];
    }
}

And I'm calling this method from the viewDidLoad:

- (void)viewDidLoad
   {
      [self switchOnorOff];
   }

My issue is the above code doesn't animate the imageView.

But when I tried the below code it works:

[self performSelectorOnMainThread:@selector(animateTheImageview:) withObject:self.lightImage waitUntilDone:YES];

My question is why this issue is happening ? Is there any difference between,

[self performSelectorOnMainThread:@selector(animateTheImageview:) withObject:self.lightImage waitUntilDone:YES];

and

[self animateTheImageview:self.lightImage];

Susy

Answer 1

You should not perform any animation in the viewDidLoad, and also call [super viewDidLoad] in it since you're just overriding it. Try displaying it on viewWillAppear or viewDidAppear.

Then, according to the NSObject Reference, performSelectorOnMainThread:withObject:waitUntilDone:

queues the message on the run loop of the main thread

So the other messages on queue may complete first before performing the animation.

Hope this helps

Aramenta

Thank you, had same problem when placing animations in viewDidLoad inside pageViewController. – Sikora