iphone - CGAffineTransformMakeRotation counter clockwise always

Question

I an trying to animate a UIImageView to rotate counter clockwise when a user touches it and moves its finger on it in clockwise direction.
Basically I want the UIImageView to go back to its original position once the touch ends and it should move in counter clockwise direction.

The problem I have is that every time angle (in degrees) is greater than 180 then the image rotates clockwise back to its original position. Its apparently taking the shortest path back. As for angles 179 degrees or less the image rotate counter clockwise (what i need).

I tried both these pieces of code and they behave the same way. Any suggestions?

NOTE: here angle variable is a double and its initialized to be zero and it remains 0 throughout my code

-(void) touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event 
{
    [self handleObject:touches withEvent:event isLast:YES];

    /* this doesn't make rotation counter clockwise for rotations greater than 180 */
    [UIView beginAnimations:nil context:NULL];
    [UIView setAnimationCurve: UIViewAnimationCurveLinear];
    [UIView setAnimationDuration:1.0];
    [UIView setAnimationRepeatCount:1]; 
    CGAffineTransform transform = CGAffineTransformMakeRotation(angle);
    circle1ImgVw.transform = CGAffineTransformRotate(transform, angle);
    // ends animation
    [UIView commitAnimations];


    /* this doesn't make rotation counter clockwise for rotations greater than 180 */
    [UIView animateWithDuration:1.0 animations:^{
            circle1ImgVw.transform = CGAffineTransformMakeRotation(angle);
        }];
} 

I tried looking into this post and there are couple of problems with it

• I cannot touch and rotate the image anymore after the animation is done
• It always animates in clockwise direction and I haven't been able to figure out how to make it go counter clockwise smoothly from the point where the user ended rotating the image.

Answer 1

I had a similar issue, check the accepted answer out, it might help you:

Rotate a UIView clockwise for an angle greater than 180 degrees

---

In response to comments, maybe this will help:

In my code I actually use

rotationAnimation.fromValue
rotationAnimation.toValue

instead of

rotationAnimation.byValue.

The rotation is always going to be counter clockwise if the toValue is less than the fromValue. It doesn't matter if your values are positive or negative, only the relation between them.

Figure out what your starting angle is, figure out which direction you want to rotate and figure out what your ending angle is. Make sure that it's less than your starting angle if you want to go counter clockwise. Here is the code I use for animating a clock hand clockwise from 12:00 to the current time.

-(void) viewDidAppear:(BOOL)animated
{
    [super viewDidAppear:animated];

    [self updateClockArmAngle];
}

- (void)updateClockArmAngle
{
    // Get the time
    NSDate *date = [NSDate date];
    NSCalendar* calendar = [[[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar] autorelease];
    [calendar setTimeZone:[NSTimeZone timeZoneWithName:@"America/Toronto"]];
    NSDateComponents* components = [calendar components:(NSHourCalendarUnit | NSMinuteCalendarUnit) fromDate:date];

    CGFloat hour = [components hour];
    CGFloat angle = (hour/24.0)*(2*M_PI);

    CGFloat minute = [components minute];
    angle += (minute/(24*60))*(2*M_PI);

    [self rotateViewAnimated:self.clockArm withDuration:1.5 byAngle:angle];
}


- (void) rotateViewAnimated:(UIView*)view
               withDuration:(CFTimeInterval)duration
                    byAngle:(CGFloat)angle
{    
    CABasicAnimation *rotationAnimation;
    rotationAnimation = [CABasicAnimation animationWithKeyPath:@"transform.rotation.z"];
    rotationAnimation.fromValue = 0;
    rotationAnimation.toValue = [NSNumber numberWithFloat:angle];
    rotationAnimation.duration = duration;
    rotationAnimation.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseInEaseOut];
    [rotationAnimation setRemovedOnCompletion:NO];
    [rotationAnimation setFillMode:kCAFillModeForwards];
    [view.layer addAnimation:rotationAnimation forKey:@"rotationAnimation"];
}