如何获取CAKeyframeAnimation对象的当前屏幕xy位置?
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在ios 12 beta 12下的Swift 4.2中,我想得到一个点的当前位置,我在CAKeyframeAnimation
的路径上进行了动画处理。
动画的代码是这样的:
@IBOutlet weak var dot: UIImageView!
func animateDot()
// Oval path.
let ovalWidth = UIScreen.main.bounds.width * 0.7
let ovalHeight = UIScreen.main.bounds.height * 0.75
let ovalPath = UIBezierPath(ovalIn: CGRect(x: -ovalWidth / 2 , y: -ovalHeight / 2, width: ovalWidth, height: ovalHeight))
let orbit = CAKeyframeAnimation(keyPath: "position")
orbit.path = ovalPath.cgPath
orbit.duration = CFTimeInterval(2.5)
orbit.isAdditive = true
orbit.repeatCount = 6
orbit.calculationMode = kCAAnimationPaced
orbit.rotationMode = kCAAnimationRotateAuto
self.dot.layer.add(orbit, forKey: "orbit")
我的问题是:一旦启动并运行,我怎样才能在Swift中查询动画以获得点中心的当前屏幕xy?
答案
我发现可以查询与点关联的活动表示层以获取绑定点的当前位置的帧:
if (self.dot.layer.presentation() != nil)
let dotLocation = self.dot.layer.presentation()?.frame
os_log("self.dot.layer.presentation()?.frame.minX %12f", type: .debug, dotLocation!.minX)
os_log("self.dot.layer.presentation()?.frame.maxX %12f", type: .debug, dotLocation!.maxX)
os_log("self.dot.layer.presentation()?.frame.minY %12f", type: .debug, dotLocation!.minY)
os_log("self.dot.layer.presentation()?.frame.maxY %12f", type: .debug, dotLocation!.maxY)
var dotScreenLocation: CGPoint = CGPoint(x: 0, y: 0)
dotScreenLocation.x = dotLocation!.minX + ((dotLocation!.maxX - dotLocation!.minX) / 2)
dotScreenLocation.y = dotLocation!.minY + ((dotLocation!.maxY - dotLocation!.minY) / 2)
os_log("self.dot.layer.presentation()?.frame center x,y %12f,%12f", type: .debug, dotScreenLocation.x, dotScreenLocation.y)
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