I'm an adventurer, so I tried this:
=======
self.backgroundLayer.contents = nsImage;
CABasicAnimation * crossfade;
crossfade = [CABasicAnimation animationWithKeyPath: @"contents"];
crossfade.duration = 2.0;
crossfade.removedOnCompletion = YES;
[self.backgroundLayer addAnimation: crossfade forKey: nil];
=======
This works as I expect: The contents of the layer transition smoothly, without
flicker.
— F
On 15 Jul 2012, at 4:08 PM, Fritz Anderson wrote:
> 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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