Re: CALayer/CAAnimation doesn't animate

FROM : Bill Dudney
DATE : Tue Jan 15 21:54:04 2008

Hi Joachim,


On Jan 15, 2008, at 7:38 AM, Joachim wrote:

> Bill, Scott,
>
> Thanks for setting this straight! This was a great help. Having read 
> the documentation numerous times, I still wasn't clear on how to add 
> my own root layer in a layer-hosting view. I thought I could "reuse" 
> the layer-backed view layer, set in IB and/or code. Apparently not. 
> Also, animating the wrong property doesn't exactly make things 
> happen either. :-)
>
> The reason I use a layer-hosted view and explicit animations is 
> because I need some more complicated animations to happen and 
> several of them. As many as 30-40 layers animating at a time. The 
> code below is just to make even a simple animation work for me.
>
> I now got the layer to move, but a few more problems remain...
>
> - (void)animateNewLayer
> {
>    // Create animating layer
>    CALayer *layer = [CALayer layer];
>
>    // Configure layer
>    layer.anchorPoint = CGPointMake (0, 0); // Use lower/left corner 
> as with views
>    layer.frame = CGRectMake (0, 0, 24, 24);
>    layer.contents = myCGImageRef; // Created earlier in this method
>    CGImageRelease (myCGImageRef);
>
>    // If we don't have a root layer, create and set it
>    if (!self.layer) {
>        [self setLayer:[CALayer layer]];
>        [self setWantsLayer:YES];
>    }
>    [[self layer] addSublayer:layer]; // Add our animating sublayer
>
>    // Create animation
>    CABasicAnimation *anim = [CABasicAnimation 
> animationWithKeyPath:@"position"];
>
>    // Configure animation
>    anim.fromValue      = [NSValue valueWithPoint:NSMakePoint (0, 0)];
>    anim.toValue        = [NSValue valueWithPoint:NSMakePoint (100, 
> 100)];
>    anim.timingFunction = [CAMediaTimingFunction 
> functionWithName:kCAMediaTimingFunctionEaseInEaseOut];
>    anim.duration      = 2.0;
>    animation.fillMode  = kCAFillModeForwards;
>    anim.delegate      = self;
>
>    // Add animation to layer; also triggers the animation
>    [layer addAnimation:anim forKey:@"position"];
> }
>
> I think I'm now setting the root layer as I should. If the root 
> layer doesn't exist, I create and add it to the hosting view and 
> then add and remove sublayers in the lifetime of the view as needed. 
> The hosting view never goes away, and so neither does the root layer 
> once it's added.
>
> These are the problems I see:
>
> 1) When the layer starts animating, the hosting view dissapears and 
> never reappears (this also happened in the original code)


Hm... are you drawing into the view? That is another no-no, once you 
take over the layer of a view you should not draw in it (with the 
drawRect: method) but instead do all your drawing via the layer.

>
> 2) Setting the fillMode to kCAFillModeForwards still makes the layer 
> jump back to its original position (or opacity or whatever I animate 
> on) after the animation is done


Not sure what this is all about. Are you ever setting the value or 
just depending on the animation to set it for you?

>
>
> Once again, thank you for taking the time.


my pleasure - HTH,


-bd-
http://bill.dudney.net/roller/objc


>
>
> Joachim
>
>
> On 15-Jan-08, at 9:10 AM, Scott Anguish wrote:
>

>> On Jan 14, 2008, at 6:07 PM, Bill Dudney wrote:
>>

>>> Hi Joachim,
>>>
>>> You should not be manipulating the layer that the view creates for 
>>> its self as a general rule.

>>
>> True.
>>
>> If you don't create it and set it, you shoudn't mess with it.
>>

>>> If you call [self setLayer:[CALayer layer]] right before you call 
>>> [self setWantsLayer:YES] you should start to see behavior that 
>>> more closely matches what you want/expect.

>>
>> This is how you should always do it.  Set the layer to your 
>> requested layer class, then enabled layers.
>>
>> But, no, you won't see the behavior you expect.
>>

>>>  CABasicAnimation *anim = [CABasicAnimation 
>>> animationWithKeyPath:@"frameOrigin"];
>>>
>>>  // Configure animation
>>>  anim.fromValue      = [NSValue valueWithPoint:NSMakePoint (0, 0)];
>>>  anim.toValue        = [NSValue valueWithPoint:NSMakePoint (100, 
>>> 100)];
>>>  anim.timingFunction = [CAMediaTimingFunction 
>>> functionWithName:kCAMediaTimingFunctionEaseInEaseOut];
>>>  anim.duration      = 2.0;
>>>  anim.delegate      = self;
>>>
>>>  // Add animation to layer; also triggers the animation
>>>  [layer addAnimation:anim forKey:@"frameOrigin"];

>>
>> oints 1 - frameOrigin isn't a property of CALayer.  position is. 
>> You can only animate properties of a layer that exist, and that are 
>> marked as animatable in the CALayer class. conceptual doc does 
>> cover this.  Perhaps you're confusing with the view frameOrigin 
>> method?
>>
>> point 2 - you're using explicit animation and you're using the 
>> default fillMode (kCAFillModeRemoved). This causes the explicit 
>> animation to be removed when the animation is over. So you blink, 
>> and it's gone back to the start point.
>>
>> BTW, I'm not sure you want an explicit animation in this case 
>> anyways.. you'd expect that the layer would keep its 100,100 
>> location, wouldn't you? in that case you could just use implicit 
>> animation.  If you really want the different timing function than 
>> the default you can change the implicit animation for the "frame" 
>> property.
>>
>> point 3 is because you're using the wrong delegate method if you're 
>> using animationDidStop: this isn't a CALayer delegate method. 
>> animationDidStop:finished: is.

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