Ive been struggling with this for a couple of days now.
I have a custom CALayer with a custom property, percentage. It's @dynamic and
set up to cause a redraw.
+(BOOL)needsDisplayForKey:(NSString *)key
{
return [ @"percentage" isEqualToString:key ];
}
I return CABasicAnimations for percentage and for position with the code at the
bottom in actionForKey:. The position one just makes the position change really
slowly.
For position all I have to do is make a CABasicAnimation, set the duration and
nothing else and return it, the position animates smoothly from where it was to
where it's going.
If I do the same for 'percentage', just return a CABasicAnimation with the
duration set, it doesn't animate, it just goes instantly to the final value.
For this one I have to explicitly set the 'fromValue' to the current value in
the presentation layer, leaving it nil just doesn't do the job. It finds the
'toValue' itself, but I have to tell it where it's coming from.
Why do they work differently? This prevents me from using addAnimation:forKey:
for 'percentage' because each one is different, depending what the current
value of percentage is.
-(id<CAAction>)actionForKey:(NSString *)event
{
if( [ event isEqualToString:@"position" ] )
{
CABasicAnimation *animation = [ CABasicAnimation
animationWithKeyPath:@"position" ];
animation.duration = 7.f;
return animation;
}
if( [ event isEqualToString:@"percentage" ] )
{
CABasicAnimation *animation = [ CABasicAnimation
animationWithKeyPath:@"percentage" ];
animation.duration = 2.f;
animation.fromValue = [ self.presentationLayer
valueForKey:event ];
return animation;
}
return [ super actionForKey:event ];;
}
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