UICollectionView reloadItemsAtIndexPaths奇怪的动画行为

Question

我正在使用a UICollectionView并reloadItemsAtIndexPaths实现最高效率并免费获得动画.

不知何故,动画有时只会触发(可能会导致重用单元？)我创建了一个简单的项目,其中包含一个UIViewController,一个UICollectionView和一个UIButton来帮助我触发动画.

这是我的代码:

import UIKit

class ViewController: UIViewController, UICollectionViewDataSource, UICollectionViewDelegate {
    var cells = [1]
    @IBOutlet weak var sampleCollectionView: UICollectionView!
    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.
    }
    @IBAction func buttonPressed(sender: AnyObject) {
        reloadVisibleSlides()
    }

    func reloadVisibleSlides() {

        self.sampleCollectionView.reloadItemsAtIndexPaths(self.sampleCollectionView.indexPathsForVisibleItems())

    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }


    func collectionView(collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return cells.count
    }

    func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell {

        var cell:UICollectionViewCell = collectionView.dequeueReusableCellWithReuseIdentifier("cell", forIndexPath: indexPath) as! UICollectionViewCell
        cell.backgroundColor = UIColor(hue: CGFloat(arc4random() % 256) / 256.0, saturation: 1, brightness: 1, alpha: 1)
        return cell

    }

}

如果你编译并运行它,你会看到它只是触发它.

我也试过用它来包围它 performBatchUpdates

有什么我做错了吗？还有另一种方法可以实现吗？