iOS-重力弹跳动画（流畅版）

方法一：

如果需弹跳多次，动画要多层嵌套，代码量稍微有点大，弹跳结束中心点不变。

//动画弹跳效果关键代码
弹跳多次可自行多嵌套几次   调用此方法  只需传入弹跳对象
- (void)animationShootOut:(UIView *)animationView{
    CGRect frame = animationView.frame;
    [UIView animateWithDuration:0.4f delay:0.0f options:UIViewAnimationOptionCurveEaseIn animations:^(void){
        
    } completion:^(BOOL finished){
        [UIView animateWithDuration:0.4f delay:0.0f options:UIViewAnimationOptionCurveEaseOut animations:^(void){
            //弹起
            animationView.frame = CGRectMake(frame.origin.x, frame.origin.y-20, frame.size.width, frame.size.height);
        } completion:^(BOOL finished){
            [UIView animateWithDuration:0.4f delay:0.0f options:UIViewAnimationOptionCurveEaseIn animations:^(void){
                //下降
                animationView.frame = frame;
            } completion:^(BOOL finished){
                [UIView animateWithDuration:0.4f delay:0.0f options:UIViewAnimationOptionCurveEaseOut animations:^(void){
                    //弹起
                    animationView.frame = CGRectMake(frame.origin.x, frame.origin.y-10, frame.size.width, frame.size.height);
                } completion:^(BOOL finished){
                    //下降
                    [UIView animateWithDuration:0.4f delay:0.0f options:UIViewAnimationOptionCurveEaseOut animations:^(void){
                        animationView.frame = frame;
                    } completion:^(BOOL finished){
                    }];
                }];
            }];
        }];
    }];
}

方法二：

usingSpringWithDamping：弹簧动画的阻尼值，也就是相当于摩擦力的大小，该属性的值从0.0到1.0之间，越靠近0，阻尼越小，弹动的幅度越大，反之阻尼越大，弹动的幅度越小，如果大道一定程度，会出现弹不动的情况。
initialSpringVelocity：弹簧动画的速率，或者说是动力。值越小弹簧的动力越小，弹簧拉伸的幅度越小，反之动力越大，弹簧拉伸的幅度越大。这里需要注意的是，如果设置为0，表示忽略该属性，由动画持续时间和阻尼计算动画的效果，弹跳结束后中心点下移10

    [UIView animateWithDuration:1 delay:0 usingSpringWithDamping:0.2 initialSpringVelocity:4 options:UIViewAnimationOptionAllowUserInteraction animations:^{
        CGPoint tempPoint=_btn.center;
        tempPoint.y += 10;
        _btn.center=tempPoint;
    } completion:^(BOOL finished) {
        
    }];

方法三：

弹跳结束后中心点不变，推荐使用此方法。

    // _btn调用动画效果 
    shakerAnimation(_btn, 2, 20);

// 重力弹跳动画效果
void shakerAnimation (UIView *view ,NSTimeInterval duration,float height){
    CAKeyframeAnimation * animation = [CAKeyframeAnimation animationWithKeyPath:@"transform.translation.y"];
    CGFloat currentTx = view.transform.ty;
    animation.duration = duration;
    animation.values = @[@(currentTx), @(currentTx + height), @(currentTx-height/3*2), @(currentTx + height/3*2), @(currentTx -height/3), @(currentTx + height/3), @(currentTx)];
    animation.keyTimes = @[ @(0), @(0.225), @(0.425), @(0.6), @(0.75), @(0.875), @(1) ];
    animation.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseInEaseOut];
    [view.layer addAnimation:animation forKey:@"kViewShakerAnimationKey"];
}