iOS 快速旋转动画不固定

Question

我正在尝试旋转 UIImageView。旋转动画工作正常，但在图像结束时会返回到其原始方向。下面是我用来旋转它的扩展:

extension UIView {
func rotate(duration: CFTimeInterval = 1.0, degrees:Double, completionDelegate: AnyObject? = nil) {
    let rotateAnimation = CABasicAnimation(keyPath: "transform.rotation")
    rotateAnimation.fromValue = 0.0
    let radians = CGFloat(degrees * M_PI / degrees)
    rotateAnimation.toValue = CGFloat(radians)
    rotateAnimation.duration = duration

    if let delegate: AnyObject = completionDelegate {
        rotateAnimation.delegate = delegate
    }
    self.layer.addAnimation(rotateAnimation, forKey: nil)
}

}

我已关闭自动布局。我错过了什么？

Answer 1

在直接核心动画中，您必须实际设置要设置动画的属性。单独制作动画仅显示效果，然后弹回到起始值。虽然设置 fillMode 和 removedOnCompletion 将在视觉上起作用，但图层上旋转属性的实际值仍然是原始值，而不是最终值您在动画的toValue属性中指定。最终结果仅是视觉效果。

我建议您按照 Jan 的建议使用 UIView 动画函数，或者您可以在动画中显式设置该属性，例如:

func rotate(duration: CFTimeInterval = 1.0, degrees:Double, completionDelegate: AnyObject? = nil) {
    let rotateAnimation = CABasicAnimation(keyPath: "transform.rotation")
    rotateAnimation.fromValue = 0.0
    let radians = CGFloat(degrees * M_PI / degrees)
    rotateAnimation.toValue = CGFloat(radians)
    rotateAnimation.duration = duration

    if let delegate: AnyObject = completionDelegate {
        rotateAnimation.delegate = delegate
    }
    self.layer.addAnimation(rotateAnimation, forKey: nil)

    // Actually set the layer's property
    self.layer.transform = CATransform3DMakeRotation(radians, 0.0, 0.0, 1.0)
}