Moving an object along a curve in iPhone development

Question

I wanted to animate an image object by moving it along a particular curve. It is not a general or random curve but rather a curve which follows a particular path on screen.<

Answer 1

You could use a combination of UIBezierPath and CAKeyFrameAnimation. I found a very useful blog post dealing with this subject.

http://oleb.net/blog/2010/12/animating-drawing-of-cgpath-with-cashapelayer/

Here's a simplified version of what I used (it just animates the drawing of a square):

UIBezierPath *customPath = [UIBezierPath bezierPath];
[customPath moveToPoint:CGPointMake(100,100)];
[customPath addLineToPoint:CGPointMake(200,100)];
[customPath addLineToPoint:CGPointMake(200,200)];
[customPath addLineToPoint:CGPointMake(100,200)];
[customPath addLineToPoint:CGPointMake(100,100)];

UIImage *movingImage = [UIImage imageNamed:@"foo.png"];
CALayer *movingLayer = [CALayer layer];
movingLayer.contents = (id)movingImage.CGImage;
movingLayer.anchorPoint = CGPointZero;
movingLayer.frame = CGRectMake(0.0f, 0.0f, movingImage.size.width, movingImage.size.height);
[self.view.layer addSublayer:movingLayer];

CAKeyframeAnimation *pathAnimation = [CAKeyframeAnimation animationWithKeyPath:@"position"];
pathAnimation.duration = 4.0f;
pathAnimation.path = customPath.CGPath;
pathAnimation.calculationMode = kCAAnimationLinear;
[movingLayer addAnimation:pathAnimation forKey:@"movingAnimation"];