How to use CAKeyframeAnimation for iOS Bouncing effect

Question

I made this code to create a CAKeyframeAnimation, but the result doesn't bounce at all

-(CAKeyframeAnimation *)keyframeBounceAnimationFrom:(NSValue *)from to:(NSValue *)to forKeypath:(NSString *)keyPath withDuration:(CFTimeInterval)duration { CAKeyframeAnimation * animation = [CAKeyframeAnimation animationWithKeyPath:keyPath]; NSMutableArray * valuesArray = [NSMutableArray array]; NSMutableArray * timeKeyArray = [NSMutableArray array]; [self createBounceFrom:from to:to Values:valuesArray keyTimes:timeKeyArray]; [animation setValues:valuesArray]; [animation setKeyTimes:timeKeyArray]; animation.duration = duration; return animation; } -(void)createBounceFrom:(NSValue *)from to:(NSValue *)to Values:(NSMutableArray *)values keyTimes:(NSMutableArray *)keyTimes { CGPoint toPoint= [to CGPointValue]; CGFloat offset = 60; CGFloat duration = 1.0f; NSUInteger numberOfOscillations= 4; [values addObject:from]; [keyTimes addObject:[NSNumber numberWithFloat:0.0f]]; //============ //ideally bouncing will depend from starting position to end poisiton as simulating real Dumping Oscillations //============ for (NSUInteger index= 0; index <numberOfOscillations ; index++) { CGPoint viaPoint = CGPointMake(toPoint.x, toPoint.y + offset); NSValue * via = [NSValue valueWithCGPoint:viaPoint]; [values addObject:via]; //add time consumed for each oscillation [keyTimes addObject:[NSNumber numberWithFloat:duration]]; // duration = duration - 0.1; offset = - offset ; } [values addObject:to]; [keyTimes addObject:[NSNumber numberWithFloat:0.6]]; } 

Answer 1

Here is a great link with some examples of how to use it:

(After some searching, I found this: http://www.cocoanetics.com/2012/06/lets-bounce/ , which, in my opinion, bounces much better, but is more advanced. The code is here)

http://www.touchwonders.com/some-techniques-for-bouncing-animations-in-ios/

An example with CAKeyframeAnimation would be: (taken from link)

 -(void)animateGreenBall { NSValue * from = [NSNumber numberWithFloat:greenBall.layer.position.y]; CGFloat bounceDistance = 20.0; CGFloat direction = (greenUp? 1 : -1); NSValue * via = [NSNumber numberWithFloat:(greenUp ? HEIGHT_DOWN : HEIGHT_UP) + direction*bounceDistance]; NSValue * to = greenUp ? [NSNumber numberWithFloat:HEIGHT_DOWN] : [NSNumber numberWithFloat:HEIGHT_UP]; NSString * keypath = @"position.y"; [greenBall.layer addAnimation:[self keyframeBounceAnimationFrom:from via:via to:to forKeypath:keypath withDuration:.6] forKey:@"bounce"]; [greenBall.layer setValue:to forKeyPath:keypath]; greenUp = !greenUp; } -(CAKeyframeAnimation *)keyframeBounceAnimationFrom:(NSValue *)from via:(NSValue *)via to:(NSValue *)to forKeypath:(NSString *)keyPath withDuration:(CFTimeInterval)duration { CAKeyframeAnimation * animation = [CAKeyframeAnimation animationWithKeyPath:keyPath]; [animation setValues:[NSArray arrayWithObjects:from, via, to, nil]]; [animation setKeyTimes:[NSArray arrayWithObjects:[NSNumber numberWithFloat:0.0], [NSNumber numberWithFloat:.7], [NSNumber numberWithFloat:1.0], nil]]; animation.duration = duration; return animation; }