Question

I have some objects in a view that I want to move around their own points on a screen. I want them to appear almost stationary, but with a slight circular motion (not rotation, the items will remain straight and level), kind of like a buoy bobbing up and down in the ocean with some horizontal movement as well.

My basic thought is to move the anchor point around the object. I only want a subtle effect, the objects won’t be moving around the whole screen. At most 10-20 points. They will be UIButtons still capable of being pressed. So far everything I’ve searched for results in rotation about a point, and not what I’m after.

Answer 1

You can use CAKeyframeAnimation to make your object follow a small circle or any other path that suits your needs. Here is how you create and use a CAKeyframeAnimation object.

CAKeyframeAnimation *pathAnimation = [CAKeyframeAnimation animationWithKeyPath:@"position"];
pathAnimation.calculationMode = kCAAnimationPaced;
pathAnimation.fillMode = kCAFillModeForwards;
pathAnimation.removedOnCompletion = NO;
CGMutablePathRef * circle = CGPathCreateWithEllipseInRect(CGRectMake(/* the center of your object and the radius of your circle*/));
pathAnimation.path = circle;
CGPathRelease(circle);
[buttonView.layer addAnimation:pathAnimation forKey:@"animatePath"];

This should get you started. Please note you need to import QuartzCore framework in order for this to work.