Rotate button around center

Question

Hi,

I'm searching for a way to create a menu in an iPhone app that allows buttons to rotate around a center point. To put this in visual terms: the buttons would be planets and the center is the sun.

• this would allow the user to 'spin' the buttons around the circular path.

** an actual example of this would be the Poynt menu for their iPhone app. **

I got started with this code, that I found from a post by mahboudz here on SO:

- (void) runSpinAnimationWithDuration:(UIView*)animatedView withDuration:(CGFloat) duration;
{
CABasicAnimation* rotationAnimation;
rotationAnimation = [CABasicAnimation animationWithKeyPath:@"transform.rotation.y"];
rotationAnimation.toValue = [NSNumber numberWithFloat: M_PI * 2.0 /* full rotation*/ * 1 * duration ];
rotationAnimation.duration = duration;
rotationAnimation.cumulative = YES;
rotationAnimation.repeatCount = 1.0; 
rotationAnimation.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseOut];
[animatedView.layer  setAnchorPoint:CGPointMake( 0.5, 0.5 )];
[animatedView.layer addAnimation:rotationAnimation forKey:@"rotationAnimation"];
}

There is an interesting post on rotation here on SO: link text

Anyway, I can rotate a button - but not around a predetermined path (like the planet scenario).

Any help would be appreciated.

Answer 1

You are rotating the button around it's own center, as defined by "frame" property. Additionally, you need to change the frame of the button to a different coordinate at the same time you are rotating it. Something like this:

CGFloat angle = rotationAnimation.toValue;
CGFloat radius = 50;
CGPoint rotationCenter = CGPointMake(100,100); 
b.frame = CGRectMake(rotationCenter.x + radius * cos(angle),  rotationCenter.y + radius * sin(angle), b.frame.size.width, b.frame.size.height)