Question

基本上我只是在imageView上添加一个简单的旋转动画，它是UICollectionViewCell的子视图，动画效果很好，但是当我滚动集合视图并向后滚动时，动画就停止了。如何解决这个问题呢？这是我添加到imageView的内容。

let rotationAnimation = CABasicAnimation(keyPath: "transform.rotation")
rotationAnimation.fromValue = 0.0
rotationAnimation.toValue = Double.pi
rotationAnimation.duration = 2.0
rotationAnimation.repeatCount = .infinity
view.layer.add(rotationAnimation, forKey: nil)

Answer 1

为了避免滚动的影响，需要使用Runloop及其commonModes，使用CADisplayLink制作动画可以做到：

private var _displayLinkForRotation:CADisplayLink?
var displayLinkForRotation:CADisplayLink {
    get{
        if _displayLinkForRotation == nil {
            _displayLinkForRotation = CADisplayLink(target: self, selector: #selector(excuteAnimations))
            _displayLinkForRotation?.add(to: RunLoop.current, forMode: RunLoopMode.commonModes)
        }
        return _displayLinkForRotation!
    }
}

func excuteAnimations() {
    //This function will be called 60 times per second.
    //According to your question, you have 2 seconds to rotate the view to 180 angle. So we rotate 90 angle per second here.
    //self.view could be replaced by another view you want to rotate.
    self.view.transform = self.view.transform.rotated(by: 90.0 / 60.0 / 180.0 * CGFloat.pi)

    let angle = atan2(self.view.transform.b, self.view.transform.a) * (45.0/atan(1.0))
    if (round(angle) >= 180.0) { //Stop when rotated 180 angle
        self.displayLinkForRotation.isPaused = true
    }
}

开始动画：

self.displayLinkForRotation.isPaused = false

摧毁它：

self.displayLinkForRotation.invalidate()
_displayLinkForRotation = nil

Answer 2

因为您没有为初始化rotationAnimation时使用的动画添加键改变行

view.layer.add(rotationAnimation, forKey: nil)

到

view.layer.add(rotationAnimation, forKey: "transform.rotation")

希望有所帮助

如何使动画在UICollectionView上运行

2 个答案: