Question

I’m pretty sure this is a rather simple and straightforward question for anyone that has ever tried this before , but i’m kind of a newbie to what you would call “advanced” animation.

I’m trying to create the following movement of an object by using CAKeyframeAnimation (with “position” key path)

http://www.sumopaint.com/files/images800/aeegfexznpohlehd.jpg

I’ve tried setting the path with a UIBezierPath but got confused and frustrated pretty fast with not finding the logic behind it 🙂

I’d love to hear if you have an opinion about this…

This is my base code (which might as well be written from scratch if a better idea would occur :P)

Also i wanted to fade out the object on completion. is there such a selector that performs on animation completion? (such as [UIView animateWithDuration] ) ?

UIBezierPath *thumbPath = [UIBezierPath bezierPath];
[thumbPath moveToPoint: P(99,270)];
[thumbPath addCurveToPoint:P(164,260) controlPoint1:P(164,280) controlPoint2:P(164,280)];
[thumbPath addCurveToPoint:P(164,260) controlPoint1:P(260,310) controlPoint2:P(260,310)];

CAKeyframeAnimation *pathAnimation = [CAKeyframeAnimation animationWithKeyPath:@"position"];
pathAnimation.path = thumbPath.CGPath;
pathAnimation.duration = 2.0;

Answer 1

Just wanted to share the simplest way i’ve found for doing this, for anyone who is a noob in CAAnimation such as myself.

Instead of using a UIBezierPath , i’ve just manually written the points on screen (x,y) for the path, and than created a path using those, thus creating the needed curve. Very useful and easy.

Hope you find this helpful:

NSArray *myPoints = [NSArray arrayWithObjects: 
                             [NSValue valueWithCGPoint:P(77,287)],
                             [NSValue valueWithCGPoint:P(97,270)],
                             [NSValue valueWithCGPoint:P(112,260)],
                             [NSValue valueWithCGPoint:P(130,250)],
                             [NSValue valueWithCGPoint:P(154,245)],
                             [NSValue valueWithCGPoint:P(174,250)],
                             [NSValue valueWithCGPoint:P(193,260)],
                             [NSValue valueWithCGPoint:P(210,270)],
                             [NSValue valueWithCGPoint:P(231,287)],
                             nil];

CGMutablePathRef path = CGPathCreateMutable();
CGPathMoveToPoint(path, NULL, 77, 280);

for(NSValue *val in myPoints){
    CGPoint p = [val CGPointValue];
    CGPathAddLineToPoint(path, NULL, p.x, p.y);
}

CAKeyframeAnimation *pathAnimation = [CAKeyframeAnimation animationWithKeyPath:@"position"];
pathAnimation.path = path;
CGPathRelease(path);