CODEWITHSUNDEEP
iosuicollectionview
Xie
Xie

Reputation: 627

How to keep animation working on UICollectionView

Basically I just add a simple rotate animation on an imageView which is a subview of UICollectionViewCell, the animation works fine, but when I scroll the collection view and scroll back, the animation just stoped. How to solve this problem? This is what I added to the imageView.

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)

Upvotes: 0

Views: 362

Answers (2)

Vanita L.
Vanita L.

Reputation: 1325

Because you have not added key for animation, which you used when initialising rotationAnimation change line

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

to

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

Hope it helps

Upvotes: 0

Yun CHEN
Yun CHEN

Reputation: 6648

To avoid scrolling's influence, need to use Runloop and its commonModes, making animation with CADisplayLink can do it:

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
    }
}

To start animation:

self.displayLinkForRotation.isPaused = false

To destroy it:

self.displayLinkForRotation.invalidate()
_displayLinkForRotation = nil

Upvotes: 1

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