iOS动画：动画立即停止inovoke

Question

我想在图层上的图像上实现3D漫游，但它不起作用。 我发现动画在开始时立即停止了函数调用。所以我认为这就是动画不起作用的原因。

以下是我的代码：

override func viewDidLoad() {
    super.viewDidLoad()
    self.view.backgroundColor = UIColor.white

    // Do any additional setup after loading the view.

    let doorLayer = CALayer()
    doorLayer.frame = CGRect(x: 0, y: 0, width: 128, height: 256)
    doorLayer.position = CGPoint(x: 150 - 64, y: 150)
    doorLayer.anchorPoint = CGPoint(x: 0, y: 0.5)
    doorLayer.contents = UIImage(named: "door")?.cgImage
    self.view.layer.addSublayer(doorLayer)

    var perspective = CATransform3DIdentity
    perspective.m34 = -1.0 / 500.0
    self.view.layer.sublayerTransform = perspective

    let animation = CABasicAnimation()
    animation.keyPath = "transform.rotation.y"
    animation.toValue = -Double.pi/2
    animation.duration = 2.0
    animation.repeatCount = 5
    animation.autoreverses = true
    animation.delegate = self
    doorLayer.add(animation, forKey: "rotationAnimation")

}
func animationDidStop(_ anim: CAAnimation, finished flag: Bool) {
    print(#function)
}

视图显示时，消息立即显示。 我该怎么办？