无限旋转UIView并暂停/停止动画,保持状态,并从当前状态继续旋转

Question

我很难尝试暂停并从旋转的当前状态继续任何UIView旋转技术.

尝试:

CGAffineTransformRotate
CGAffineTransformMakeRotation
CATransform3DMakeRotation
CABasicAnimation

基本上,如果我打电话view.layer.removeAllAnimations()或,layer.speed = 0他们都重置当前的旋转度.

还试图快照视图以使用图像而不是真正的旋转,但没有运气,因为快照忽略了旋转.

Answer 1

最后得到它,在SO上有多个答案,很多在objective-c中,将它们放在一个UIView扩展中,甚至记录在案:

extension UIView {

        /**
         Will rotate `self` for ever.

         - Parameter duration: The duration in seconds of a complete rotation (360º).
         - Parameter clockwise: If false, will rotate counter-clockwise.
         */
        func startRotating(duration duration: Double, clockwise: Bool) {
            let kAnimationKey = "rotation"
            var currentState = CGFloat(0)

            // Get current state
            if let presentationLayer = layer.presentationLayer(), zValue = presentationLayer.valueForKeyPath("transform.rotation.z"){
                currentState = CGFloat(zValue.floatValue)
            }

            if self.layer.animationForKey(kAnimationKey) == nil {
                let animate = CABasicAnimation(keyPath: "transform.rotation")
                animate.duration = duration
                animate.repeatCount = Float.infinity
                animate.fromValue = currentState //Should the value be nil, will start from 0 a.k.a. "the beginning".
                animate.byValue = clockwise ? Float(M_PI * 2.0) : -Float(M_PI * 2.0)
                self.layer.addAnimation(animate, forKey: kAnimationKey)
            }
        }

        /// Will stop a `startRotating(duration: _, clockwise: _)` instance.
        func stopRotating() {
            let kAnimationKey = "rotation"
            var currentState = CGFloat(0)

            // Get current state
            if let presentationLayer = layer.presentationLayer(), zValue = presentationLayer.valueForKeyPath("transform.rotation.z"){
                currentState = CGFloat(zValue.floatValue)
            }

            if self.layer.animationForKey(kAnimationKey) != nil {
                self.layer.removeAnimationForKey(kAnimationKey)
            }

            // Leave self as it was when stopped.
            layer.transform = CATransform3DMakeRotation(currentState, 0, 0, 1)
        }

    }

使用它yourView.startRotating(duration: 1, clockwise: true),稍后停止做yourView.stopRotating().