滚动时，我的自定义collectionView不稳定

Question

请将文档目录中的图像加载到collectionView时创建自定义collectionView我无法快速滚动自定义collectionView滚动时看起来不稳定我不知道为什么？ 请有人能告诉我这个问题在做什么

以下我的代码：

func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell {
    let cell = collectionView.dequeueReusableCellWithReuseIdentifier("Cell", forIndexPath: indexPath) as! AlbumImagesCollectionViewCell


    if dictionaryOfSelectItem.count > 0 {
        if dictionaryOfSelectItem[indexPath.row] == indexPath.row {
            cell.imageViewCheck.image = UIImage(named: "check.png")
        }else {
            cell.imageViewCheck.image = nil
        }

    }

        cell.imageViewCheck.image = nil
        dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0)) {
        dispatch_sync(dispatch_get_main_queue(), {
            if self.arrayOfImageUrl2.count > 0 && self.arrayOfImagesFromDocumentDirectory.count > 0 {
                cell.imageViewCell.image = self.ResizeImage(self.arrayOfImagesFromDocumentDirectory[indexPath.row], targetSize: CGSize(width: 140.0, height: 140.0))
                cell.imageUrlLabel.text = self.arrayOfImageUrl2[indexPath.row]
            }

        })
    }

    return cell

}

谢谢你提前