Can I use CGAffineTransformMakeRotation to rotate a view more than 360 degrees?

Question

I'm writing an iPhone app, and I've got an image which I'ld like to have swirl outwards.

Currently my code looks like this (wrapped in a beginAnimations/commitAnimations block):

scale = CGAffineTransformScale(CGAffineTransformIdentity, 5.0f, 5.0f);
swirl = CGAffineTransformRotate(scale, M_PI);
[player setTransform:swirl];    
[player setAlpha:0.0f];

But I find that if I try to change the angle of the rotation to, say, 4*M_PI, it doesn't rotate at all. Is it possible to get a 720˚ rotation using CGAffineTransformRotate, or do I have to switch to another technology?

If I have to switch to another technology, would you recommend using another thread (or a timer) to do the animation myself, or would OpenGL be a better route to go?

Thanks,
Blake.

Answer 1

You can rotate a view, by some number of radians, regardless of whether it is less than a full rotation or many multiples of a full rotation, without having to split the rotation into pieces. As an example, the following code will spin a view, once per second, for a specified number of seconds. You can easily modify it to spin a view by a certain number of rotations, or by some number of radians.

- (void) runSpinAnimationWithDuration:(CGFloat) duration;
{
    CABasicAnimation* rotationAnimation;
    rotationAnimation = [CABasicAnimation animationWithKeyPath:@"transform.rotation.z"];
    rotationAnimation.toValue = [NSNumber numberWithFloat: M_PI * 2.0 /* full rotation*/ * rotations * duration ];
    rotationAnimation.duration = duration;
    rotationAnimation.cumulative = YES;
    rotationAnimation.repeatCount = 1.0; 
    rotationAnimation.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseOut];

    [myView.layer addAnimation:rotationAnimation forKey:@"rotationAnimation"];
}