CA crossfade
CA crossfade
- Subject: CA crossfade
- From: Fritz Anderson <email@hidden>
- Date: Sun, 15 Jul 2012 16:08:17 -0500
10.7 SDK, 10.7 target. The content view of the window is layer-hosting, containing only a CALayer.
I'm trying to crossfade the contents image of the CALayer from Image A (the existing contents) to Image B (the new contents). Surely this is simple. I'm thrashing.
Here is an excerpt from my controller object's set-image method. I've seen the following code (more or less) in responses on the Web, and it has always met with apparent satisfaction, but it does not work as I intend: Image A is instantly replaced by Image B, then the crossfade from A to B runs. Image B remains.
=====
// Initialize nsImage with the new contents.
CABasicAnimation * crossfade;
crossfade = [CABasicAnimation animationWithKeyPath: @"contents"];
crossfade.duration = 0.75;
crossfade.removedOnCompletion = YES;
crossfade.fromValue = self.backgroundLayer.contents;
crossfade.toValue = nsImage;
[self.backgroundLayer addAnimation: crossfade forKey: nil];
self.backgroundLayer.contents = nsImage;
=====
Commenting-out the assignments to .fromValue and .toValue yields the same effect.
Okay, try this: add
crossfade.delegate = self;
before the addAnimation:, and delete
self.backgroundLayer.contents = nsImage;
Add the delegate method:
- (void) animationDidStop:(CAAnimation *)anim finished:(BOOL)flag
{
NSImage * newImage = [(CABasicAnimation *)anim toValue];
self.backgroundLayer.contents = newImage;
}
Printing the nsImage pointer in the set-image method and newImage in the animationDidStop: method shows that the two pointers are equal.
In this case, the animation runs from Image A to Image B, then jumps to Image A, then jumps to Image B.
In all cases, self.backgroundLayer.actions is nil.
I'm thrashing at a task that ought to be simple and obvious. What am I missing?
— F
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