CAKeyframeAnimation and sprite sheet animation problem

I have a CAKeyframeAnimation of a sprite sheet's contentsRects property to show an animation in a CALayer. Everything works most of the time, but occasionally I see a wrong part of sprite sheet for a one frame. CAKeyframeAnimation is set to discrete mode and all the coordinates are checked. Seems to me that once in a while CAKeyframeAnimation misses a keyframe and shows me just a center piece of my sprite sheet instead of a piece that it suppose to cut out based 开发者_JAVA技巧on provided array of contensRects. How to fix the above? Also on the same topic how to debug CAKeyframeAnimation in general and find out what's going on?

thanks!

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to fix it I've wrapped my animation in CATransaction and temporarily disabled all layer actions:

[CATransaction begin];
[CATransaction setValue:(id)kCFBooleanTrue forKey:kCATransactionDisableActions]; // we need to disable all layer actions temporarily

.............. the rest of animation code ...............

[CATransaction commit];

thank you Apple's documentation!