如何使用 CAKeyframeAnimation 用于弹跳效果 IOS

Question

我制作了这段代码来创建 CAKeyframeAnimation 但结果根本没有弹跳

-(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

这是一个很好的链接，其中包含一些如何使用它的示例：

（经过更多查看，我发现了这个：http://www.cocoanetics.com/2012/06/lets-bounce/，我认为它可以产生更好的反弹，但更高级。所以不会将代码放在这里）

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

CAKeyframeAnimation 的示例如下：（取自链接）

-(void)animateGreenBall
{
    NSValue *from = @(greenBall.layer.position.y);
    CGFloat bounceDistance = 20.0;
    CGFloat direction = (greenUp? 1 : -1);

    NSValue *via = @((greenUp ? HEIGHT_DOWN : HEIGHT_UP) + direction*bounceDistance);
    NSValue *to = greenUp ? @(HEIGHT_DOWN) : @(HEIGHT_UP);
    NSString *keyPath = @"position.y";
    CAKeyframeAnimation *animation = [self keyframeBounceAnimationFrom:from
                                                                   via:via
                                                                    to:to
                                                            forKeyPath:keyPath
                                                          withDuration:.6];

    [greenBall.layer addAnimation:animation 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:@[from, via, to, nil]];
    [animation setKeyTimes:@[@(0), @(.7), @(1), nil]];

    animation.duration = duration;
    return animation;
}