使用CAKeyframeAnimation反轉UIImageView的旋轉

Question

我正在使用以下代碼無限旋轉圖像，旋轉順時針，但我還需要它反轉旋轉到逆時針每1-2轉，然后回到順時針，如何讓它工作？

    /// Image Rotation - CAKeyframeAnimation
func rotate(imageView: UIImageView, rotationSpeed: Double) {

    let animation = CAKeyframeAnimation(keyPath: "transform.rotation.z")

    animation.duration = rotationSpeed
    animation.fillMode = CAMediaTimingFillMode.forwards
    animation.repeatCount = .infinity
    animation.values = [0, Double.pi/2, Double.pi, Double.pi*3/2, Double.pi*2]

    /// Percentage of each key frame
    let moments = [NSNumber(value: 0.0), NSNumber(value: 0.1),
                   NSNumber(value: 0.3), NSNumber(value: 0.8), NSNumber(value: 1.0)]
    animation.keyTimes = moments

    imageView.layer.add(animation, forKey: "rotate")
}

Answer 1

設置animation.autoreverses = true ，將反轉動畫。

Answer 2

對於逆時針旋轉，您可以這樣做：

self.imageView?.transform = CGAffineTransform(rotationAngle: -2*CGFloat.pi)