Keeping CAShapeLayer Mask Static During Animation

Question

I'm trying to rotate a UIImageView within a circular mask (which is set with myImageView.layer.mask). The problem is that any time I attempt to rotate said UIImageView, the mask rotates with it. Here is some code.

Setting up the mask:

    UIBezierPath *path = [UIBezierPath bezierPathWithArcCenter:CGPointMake(0, - 169)
                                                        radius:191 
                                                    startAngle:0.0
                                                      endAngle:2*M_PI 
                                                     clockwise:YES];    

    CAShapeLayer *shapeLayer  = [CAShapeLayer layer];
    [shapeLayer setFrame:myImageView.bounds];
    [shapeLayer setPath:[path CGPath]];
    myImageView.layer.mask = shapeLayer;

Animation:

[UIView animateWithDuration:kRotationTime animations:^(void){        
    myImageView.transform = CGAffineTransformMakeRotation(angle);
}];

And that's basically all there is to it. A UIImageView rotating about its own center within a fixed-position circular mask--that's the desired effect. Perhaps there is another way to structure the view hierarchy so that myImageView and the mask are siblings, but I haven't had luck going that route.

Answer 1

Put the image view into an additional plain UIView superview. Set the layer mask on the superview. Animate the image view.