iPhone - 如何为CAKeyframeAnimation制作圆形路径？

Question

我试图制作一个关键帧动画，让图像视图围绕一个圆圈飞行。我使用CGPathAddCurveToPoint来制作关键帧点。问题是图像视图总是使用最短（线性）路线。

我想有某种函数为给定半径建立一个圆弧路径。

非常感谢您的帮助。

Answer 1

这会做诡计吗？

CAKeyframeAnimation* circlePathAnimation = [CAKeyframeAnimation animationWithKeyPath:@"center"]; 

    CGMutablePathRef circularPath = CGPathCreateMutable(); 
    CGRect pathRect = ...; // some rect you define. A circle has equal width/height; radius is half the values you specify here 
    CGPathAddEllipseInRect(circularPath, NULL, pathRect); 
    spinAnimation.path = circularPath; 
    CGPathRelease(circularPath); 

您会注意到动画的关键路径是您希望绕圈飞行的UIView的中心属性。

Answer 2

CGMutablePathRef path = CGPathCreateMutable(); 
CGPathMoveToPoint(path, NULL, startPoint.x, startPoint.y); 
CGPathAddQuadCurveToPoint(path, NULL,middlePoint.x, middlePoint.y,endPoint.x,endPoint.y); 

CAKeyframeAnimation *pathAnimation = [CAKeyframeAnimation animationWithKeyPath:@"position"]; 
pathAnimation.removedOnCompletion = NO; 
pathAnimation.path = path; 
[pathAnimation setCalculationMode:kCAAnimationCubic]; 
[pathAnimation setFillMode:kCAFillModeForwards]; 
pathAnimation.duration = 2.0; 

[viewTobemoved.layer addAnimation:pathAnimation forKey:nil]; 

这个动画只使用一个贝塞尔点，使软圈从开始点到结束点时，若你想用也定义圆的，你可以参考以下链接

半径准确定义曲线

http://blog.shoguniphicus.com/2011/05/19/keyframe-animation-ios-cakeyframeanimation-objective-c/