CAAnimation with performSelector afterDelay - iphone

Question

I am messing around with a basic CAAnimation example where Im just trying to get a CALayer to rotate in a subclass of UIView. I start by making a new CALayer with a red background and inserting it into self.layer. I then make a CAAnimation that is supposed to be triggered on opacity changes and apply it to the CALayer, after which it spins as expected.
Weird thing is that if I try to apply the exact same animation using performSelector:withObject:afterDelay:, the CALayer no longer animates, although its opacity still changes. Even weirder is that if I use performSelector:withObject:afterDelay: to animate self.layer using pretty much the same code, it works.
Any ideas as to what's going on? Here is my code:
- (id)initWithFrame:(CGRect)frame {
self = [super initWithFrame:frame];
if (self) {
point = [[CAGradientLayer alloc] init];
point.backgroundColor = [UIColor redColor].CGColor;
point.bounds = CGRectMake(0.0f, 0.0f, 30.0f, 20.0f);
point.position = CGPointMake(100.0f, 100.0f);
[self.layer addSublayer:point];
[point release];
[self performSelector:#selector(test) withObject:nil afterDelay:2];
}
return self;
}
-(void)test {
[self spinLayer:point];
// [self spinLayer:self.layer]; works here
}
-(CAAnimation*)animationForSpinning {
CATransform3D transform;
transform = CATransform3DMakeRotation(M_PI/2.0, 0, 0, 1.0);
CABasicAnimation *basicAnimation = [CABasicAnimation animationWithKeyPath:#"transform"];
basicAnimation.toValue = [NSValue valueWithCATransform3D:transform];
basicAnimation.duration = 5;
basicAnimation.cumulative = NO;
basicAnimation.repeatCount = 10000;
return basicAnimation;
}
-(void)spinLayer:(CALayer*)layer {
CAAnimation *anim = [self animationForSpinning];
[layer addAnimation:anim forKey:#"opacity"];
layer.opacity = 0.6;
}
and this is my interface
#interface MyView : UIView {
CALayer *point;
}
-(void)test;
-(void)spinLayer:(CALayer*)layer;
-(CAAnimation*)animationForSpinning;
#end
Note: I am instantiating this view with a frame equal to [UIScreen mainScreen].applicationFrame from within the app delegate.

Answer 1

Change this:
[layer addAnimation:anim forKey:#"opacity"];
into this:
[layer addAnimation:anim
forKey:#"notOpacity!"];
What happens is that implicit animation layer.opacity = 0.6 overwrites you explicit animation. This happens because Core Animation uses property names when adding implicit animations.
(If you move layer.opacity = 0.6 above [layer addAnimation:anim forKey:#"opacity"]; it will also work, but layer.opacity will not get animated.)
And why it works without delay: because implicit animations are "enabled" only if layer is in the tree and been displayed.