Rotate a UIView clockwise for an angle greater than 180 degrees - iphone

Question

I'm animating a clock arm from pointing towards 12 o'clock to the current time. If it is say, 11 o'clock, I want the arm to rotate clockwise to the 11 o'clock position. But of course if I use:
CGAffineTransform rotation = CGAffineTransformMakeRotation(2*M_PI*11/12);
[UIView animateWithDuration:3.0
animations:^{
clockArm.transform = rotation;
}];
the rotation goes counterclockwise. I tried:
CGFloat angle = 2*M_PI*11/12;
CGAffineTransform firstRotation = CGAffineTransformMakeRotation(M_PI-0.001);
CGFloat firstRotationTime = 3.0*(M_PI/angle);
CGAffineTransform secondRotation = CGAffineTransformMakeRotation(angle);
CGFloat secondRotationTime = 3.0 - firstRotationTime;
[UIView animateWithDuration:firstRotationTime
delay:0.0
options:UIViewAnimationCurveLinear
animations:^{
self.clockArm1.transform = firstRotation;
}
completion:^(BOOL finished) {
[UIView animateWithDuration:secondRotationTime
delay:0.0
options:UIViewAnimationCurveLinear
animations:^{
self.clockArm1.transform = secondRotation;
}
completion:^(BOOL finished){
}];
}];
The animation does go clockwise, but it is choppy - the animation still seems to be doing a UIViewAnimationEaseInOut for the first animation. What am I doing wrong, or is there another way to accomplish what I want?

Answer 1

You can use the completion block of CATransaction to set the rotation property of the view when the animation has finished. The following function worked in my test case:
- (void) rotateViewAnimated:(UIView*)view
withDuration:(CFTimeInterval)duration
byAngle:(CGFloat)angle
{
[CATransaction begin];
CABasicAnimation *rotationAnimation;
rotationAnimation = [CABasicAnimation animationWithKeyPath:#"transform.rotation.z"];
rotationAnimation.byValue = [NSNumber numberWithFloat:angle];
rotationAnimation.duration = duration;
rotationAnimation.removedOnCompletion = YES;
[CATransaction setCompletionBlock:^{
view.transform = CGAffineTransformRotate(view.transform, angle);
}];
[view.layer addAnimation:rotationAnimation forKey:#"rotationAnimation"];
[CATransaction commit];
}
You use it like
[self rotateViewAnimated:self.clockArm1 withDuration:3.0 byAngle:2*M_PI*11./12.];

Answer 2

Thanks for #Martin R 's accepted answer. I edited a bit:
I replaced this line
rotationAnimation.removedOnCompletion = YES;
with these two lines:
rotationAnimation.removedOnCompletion = NO;
rotationAnimation.fillMode = kCAFillModeForwards;
Then, in the CompletionBlock, I added one more line:
[view.layer removeAllAnimations];
So, the code finally becomes:
- (void) rotateViewAnimated:(UIView*)view
withDuration:(CFTimeInterval)duration
byAngle:(CGFloat)angle
{
[CATransaction begin];
CABasicAnimation *rotationAnimation;
rotationAnimation = [CABasicAnimation animationWithKeyPath:#"transform.rotation.z"];
rotationAnimation.byValue = [NSNumber numberWithFloat:angle];
rotationAnimation.duration = duration;
// changed by me
rotationAnimation.removedOnCompletion = NO;
rotationAnimation.fillMode = kCAFillModeForwards;
[CATransaction setCompletionBlock:^{
view.transform = CGAffineTransformRotate(view.transform, angle);
// added by me
[view.layer removeAllAnimations]; // this is important
}];
[view.layer addAnimation:rotationAnimation forKey:#"rotationAnimation"];
[CATransaction commit];
}
My references are from:
1, https://stackoverflow.com/a/3586433/2481444
2, After rotating a CALayer using CABasicAnimation the layer jumps back to it's unrotated position

Answer 3

As mentioned in comments, try this iphone UIImageView rotation
or UIView Infinite 360 degree rotation animation?
#import <QuartzCore/QuartzCore.h>
- (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"];
}