iOS 内存警告

Question

我正在尝试使用从 Parse 数据库下载的图像填充集合视图，但我收到内存警告，然后偶尔出现崩溃。有谁知道其他应用程序如何设法呈现这么多图像而不会崩溃？有人可以告诉我如何优化我已经拥有的东西吗？以下是所有相关代码：https://gist.github.com/sungjp/99ae82dca625f0d73730

var imageCache : NSCache = NSCache()


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


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

    //In storyboard, my collection view cell has the identifier "PostCell"    
    let cell = collectionView.dequeueReusableCellWithReuseIdentifier("PostCell", forIndexPath: indexPath) as! CollectionViewCell

    //I have an array called "posts" that's filled with PFObjects that have UIImage data
    let postings: PFObject = posts[indexPath.row]

    //setting my cell's string property called "objectId" to the PFObject's ID for the purpose of caching shown below
    cell.objectId = postings.objectId! as String

    let theImage: AnyObject = postings["imageFile"] as! PFFile

    if let image = self.imageCache.objectForKey(postings.objectId!) as? UIImage {

    cell.imageView.image = image
    println("had this photo in cache")

    } else {

        theImage.getDataInBackgroundWithBlock { (imageData: NSData?, error: NSError?) -> Void in

        if error != nil {

            println("error caching or downloading image")
            return
        }

        let cellImage = UIImage(data:imageData!, scale: 1.0)
        self.imageCache.setObject(cellImage!, forKey: postings.objectId!)
        cell.imageView.image = cellImage
        println("just added another photo to cache")
        }
    }

    return cell
}


class CollectionViewCell: UICollectionViewCell {

    var objectId: String!

}

Answer 1

1. 正如@Adrian B 所说：阅读有关 Instruments 的信息。
2. 您可以考虑在保存图像之前缩小图像，或者保存一个额外的较小副本以在表格视图中显示。这取决于您需要多好的图像 - 大概是表格视图不如具有 MB 数据的全尺寸图片那么大。实际上，如果适当缩放图像，它们也会看起来更好。这本身应该可以解决延迟问题。
3. 你有你的onw缓存策略，但如果你想提高性能，试试SDWebImage（见：https://github.com/rs/SDWebImage）。该库缓存图片并异步下载。