Question

I have a problem with CAAnimationGroup. I have a view called animeView and I want to apply a 3D rotation around Y axis and a scaling transform at the same time. The rotation and scaling animations work perfectly fine separately! But when I add them to a CAAnimationGroup Non of the animations occur!

What is the problem?

CAKeyframeAnimation *rotation = [CAKeyframeAnimation animation];
CATransform3D rotationTransform = CATransform3DMakeRotation(M_PI, 0.0f, 1.0f, 0.0f);
rotationTransform.m34 = 1.0 / -500;

rotation.values = [NSArray arrayWithObjects:
                   [NSValue valueWithCATransform3D:CATransform3DMakeRotation(0.0f, 0.0f, 1.0f, 0.0f)],
                   [NSValue valueWithCATransform3D:rotationTransform],
                   [NSValue valueWithCATransform3D:CATransform3DMakeRotation(2.0*M_PI, 0.0f, 1.0f, 0.0f)] ,nil];

CAKeyframeAnimation *trans = [CAKeyframeAnimation animation];

trans.values = [NSArray arrayWithObjects:[NSValue valueWithCATransform3D:CATransform3DIdentity],[NSValue valueWithCATransform3D:CATransform3DMakeScale(0.5, 0.5, 0.5)],[NSValue valueWithCATransform3D:CATransform3DIdentity], nil];

CAAnimationGroup *group = [CAAnimationGroup animation];

group.delegate = self;
[group setAnimations: [NSArray arrayWithObjects:rotation, trans, nil]];
group.duration = 2;
group.repeatCount = 3;

[self.animView.layer addAnimation:group forKey:nil];

Answer 1

There are two things that is strange with the code you’ve provided.

1. The animations doesn’t know what property they should be changing (no key path is set)
2. Both animations are changing the transform (what value should really be used?)

The way I see it is that you have two transform key-frame animations with the same number of values (three). Therefore you should calculate the total transformation matrix (both scale and rotate in one matrix) and only add that animation to your view.

It would look something like this (I’ve added lots of comments to explain what sis happening):

// Your first rotation is 0 degrees and no scaling
CATransform3D beginTransform = CATransform3DIdentity;

// Your middle rotation is the exact one that you provided ...
CATransform3D middleTransform = CATransform3DMakeRotation(M_PI, 0.0f, 1.0f, 0.0f);
// ... but the rotation matrix is then scaled as well ...
middleTransform = CATransform3DScale(middleTransform, 0.5, 0.5, 0.5);
// ... and the perspective is set
middleTransform.m34 = 1.0 / -500;

// Your end value is rotated but not scaled
CATransform3D endTransform = CATransform3DMakeRotation(2.0*M_PI, 0.0f, 1.0f, 0.0f);

// Create a new animation that should animate the "transform" property (thus the key path "transform")
CAKeyframeAnimation *rotateAndScale = [CAKeyframeAnimation animationWithKeyPath:@"transform"];
// same configurations as your group had
[rotateAndScale setDuration:2.0];
[rotateAndScale setRepeatDuration:3.0];
[rotateAndScale setDelegate:self];
// Set the values of the transform animation (yes, both scaling and rotation in one animation)
[rotateAndScale setValues:[NSArray arrayWithObjects:
                           [NSValue valueWithCATransform3D:beginTransform], 
                           [NSValue valueWithCATransform3D:middleTransform], 
                           [NSValue valueWithCATransform3D:endTransform], nil]];

// Add the animation to the layer, no need for a group here...
[animView.layer addAnimation:rotateAndScale forKey:nil];