iphone - CATransition 动画键总是 "transition"

Question

获得了基本的 CATransition。作品。

        animationKey = @"fadeIn";

        [self.icon setImage:self.iconSelected];
        [self.shadow setAlpha:1.0];
        CATransition *transitionIn = [CATransition animation];
        transitionIn.removedOnCompletion = NO;
        transitionIn.delegate = self;
        transitionIn.duration = 1.2;
        transitionIn.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseInEaseOut];
        transitionIn.type = kCATransitionFade;

        [self.icon.layer addAnimation:transitionIn forKey:animationKey];
        [self.shadow.layer addAnimation:transitionIn forKey:animationKey];
        [CATransaction commit];

问题来了:

        [self.icon.layer animationForKey:animationKey]

总是返回 NULL。

当我这样做时:

        [self.icon.layer animationKeys]

我得到:

        icon keys: (
transition
         )

我在这里错过了什么？

Answer 1

CALayer reference说“特殊键 kCATransition 自动用于过渡动画。”