Swift：沿路径部分移动 UIImage

我正在使用此代码沿曲线移动 UIImage：

    // paint curve for sun
    let path = UIBezierPath()

    let imageSunName = "small_sun.png"
    let imageSun = UIImage(named: imageSunName)
    let imageView = UIImageView(image: imageSun!)

    imageView.frame = CGRect(x: xStart, y: yStart, width: 24, height: 24)
    self.view.addSubview(imageView)

    path.moveToPoint(CGPoint(x: xStart,y: yStart))

    path.addQuadCurveToPoint(CGPoint(x: xEnd, y: yEnd), controlPoint: CGPoint(x: xMiddleTop, y: yMiddleTop))

    let animation = CAKeyframeAnimation(keyPath: "position")
    animation.path = path.CGPath

    animation.repeatCount = 0
    animation.duration = 5.0

    imageView.layer.addAnimation(animation, forKey: "animate position along path")

尽管如此，仍然存在两个问题：

• 我想沿着路径仅部分移动图像（根据当前时间与日出/日落） - 如何做到这一点？
• 动画停止后图像跳转到其原始位置 - 如何避免这种情况？

Cheers

为了避免跳转到其原始位置，请添加：

animation.fillMode = kCAFillModeForwards
animation.removedOnCompletion = false