how to rotate CALayer at one point.

Question

how to rotate CALayer at one selected point.

@all Thanks in advance.

Answer 1

Check out the CA documentation here:

http://developer.apple.com/library/mac/#documentation/Cocoa/Reference/CoreAnimation_functions/Reference/reference.html

You want to set the transform to a CATransform3DRotate, for example:

CATransform3D current = myLayer.transform;
myLayer.transform = CATransform3DRotate(current, DEGREES_TO_RADIANS(20), 0, 1.0, 0);

Answer 2

CATransform3D transform = CATransform3DIdentity;
transform = CATransform3DTranslate(transform, rotationPoint.x-center.x, rotationPoint.y-center.y, 0.0);
transform = CATransform3DRotate(transform, rotationAngle, 0.0, 0.0, -1.0);
transform = CATransform3DTranslate(transform, center.x-rotationPoint.x, center.y-rotationPoint.y, 0.0);

Where center is the center of your layer, rotationAngle is in radians (positive is counterclockwise), and rotationPoint is the point about which you wish to rotate. center and rotationPoint are in the coordinate space of the containing view.