抛物动画

此动画在于运用 CAKeyframeAnimation 关键帧动画，以及贝塞尔关键帧动画

- (void)throwObject:(UIView *)obj fromPoint:(CGPoint)startPoint toPoint:(CGPoint)endPoint height:(CGFloat)height duration:(CGFloat)duration {

self.showingView = obj;

// 初始化抛物线 path

CGMutablePathRef path = CGPathCreateMutable();

CGFloat cpx = (startPoint.x + endPoint.x)/2;

CGFloat cpy = -height;

CGPathMoveToPoint(path, NULL, startPoint.x, startPoint.y);

CGPathAddQuadCurveToPoint(path, NULL, cpx, cpy, endPoint.x, endPoint.y);

CAKeyframeAnimation *animation = [CAKeyframeAnimation animationWithKeyPath:@"position"];

animation.path = path;

CFRelease(path);

CABasicAnimation *scaleAnimation = [CABasicAnimation animationWithKeyPath:@"transform.scale"];

scaleAnimation.autoreverses = YES;

scaleAnimation.toValue = [NSNumber numberWithFloat:(CGFloat)((arc4random()%4) + 4)/10.0];

CAAnimationGroup *groupAnimation = [CAAnimationGroup animation];

groupAnimation.delegate = self;

groupAnimation.repeatCount = 1;

groupAnimation.duration = duration;

groupAnimation.removedOnCompletion = NO;

groupAnimation.animations = @[scaleAnimation,animation];

[obj.layer addAnimation:groupAnimation forKey:@"position scale"];

}

代码地址：抛物线动画