问题描述
我为这个问题看了几个答案，但是都没有帮助。
vc1是常规vc，我从firebase抓取20张图像，在vc2中，我使用ARKit在用户选择时显示这些图像。我在vc2中有一个collectionView，可从firebase中分页另外20张图像。问题是当接下来的20张图像正在加载并且我开始滚动时，该应用程序崩溃并显示Message from debugger: Terminated due to memory issue。滚动这些新图像时，我查看了内存图，它最多拍摄了1个演出，所以这是崩溃的原因。 ARKit和我周围漂浮的节点也会导致内存增加，但这并不是造成崩溃的原因，如下所述。
1-在单元格内部，我使用SDWebImage在imageView中显示图像。一旦我注释掉SDWebImage一切正常，滚动就很流畅，并且没有更多的崩溃，但是我当然看不到图像。我切换到URLSession.shared.dataTask，并且再次出现相同的内存问题。
2-最初使用iPhone全屏相机拍摄图像，并使用jpegData(compressionQuality: 0.3).保存，像元大小为40x40。在SDWebImage完成块中，我尝试进行resize the image，但是内存崩溃仍然持续。
3-我使用Instruments> Leaks查找内存泄漏，出现了一些基金会泄漏，但是当我关闭vc2时，Deinit始终运行。在vc2内部，没有任何长时间运行的计时器或循环，我在所有闭包中都使用[weak self]。
4-正如我在第二点所述，问题肯定是imageView / image，因为一旦我从流程中将其删除，一切都会正常进行。如果我不显示任何图像，则一切正常（将出现40个红色imageView，其中没有图像）。
如何解决此问题？
for child in snapshot.children.allObjects as! [DataSnapshot] {
guard let dict = child.value as? [String:Any] else { continue }
let post = Post(dict: dict)
datasource.append(post)
let lastIndex = datasource.count - 1
let indexPath = IndexPath(item: lastIndex,section: 0)
UIView.performWithoutAnimation {
collectionView.insertItems(at: [indexPath])
}
}
cellForItem：
func collectionView(_ collectionView: UICollectionView,cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: self.cellId,for: indexPath) as! PostCell
cell.resetAll()
cell.post = dataSource[indexPath.item]
return cell
}
PostCell
private lazy var imageView: UIImageView = {
let iv = UIImageView()
iv.translatesAutoresizingMaskIntoConstraints = false
iv.contentMode = .scaleAspectFill
iv.layer.cornerRadius = 15
iv.layer.masksToBounds = true
iv.backgroundColor = .red
iv.isHidden = true
return iv
}()
private lazy var spinner: UIActivityIndicatorView = {
let actIndi = UIActivityIndicatorView(style: UIActivityIndicatorView.Style.medium) // ...
}()
var post: Post? {
didSet {
guard let urlSr = post?.urlStr,let url = URL(string: urlSr) else { return }
spinner.startAnimating()
// if I comment this out everything works fine
imageView.sd_setimage(with: url,placeholderImage: placeHolderImage,options: [],completed: {
[weak self] (image,error,cache,url) in
// in here I tried resizing the image but no diff
dispatchQueue.main.async { [weak self] in
self?.showAll()
}
})
setAnchors()
}
}
func resetAll() {
spinner.stopAnimating()
imageView.image = nil
imageView.removeFromSuperView()
imageView.isHidden = true
}
func showAll() {
spinner.stopAnimating()
imageView.isHidden = false
}
func setAnchors() {
contentView.addSubview(imageView)
imageView.addSubview(cellSpinner)
// imageView is pinned to all sides
}
解决方法
在评论中@matt是100％正确的，问题是图像对于40x40的collectionView太大，我需要调整图像的大小。由于某种原因，我问题中的调整大小链接不起作用，因此我将其用于resize image。我还使用了URLSession和这个answer
我做了10个步骤，全部注释掉了
// 0. set this anywhere outside any class
let imageCache = NSCache<AnyObject,AnyObject>()
PostCell：
private lazy var imageView: UIImageView = { ... }()
private lazy var spinner: UIActivityIndicatorView = { ... }()
// 1. override prepareForReuse,cancel the task and set it to nil,and set the imageView.image to nil so that the wrong images don't appear while scrolling
override func prepareForReuse() {
super.prepareForReuse()
task?.cancel()
task = nil
imageView.image = nil
}
// 2. add a var to start/stop a urlSession when the cell isn't on screen
private var task: URLSessionDataTask?
var post: Post? {
didSet {
guard let urlStr = post?.urlStr else { return }
spinner.startAnimating()
// 3. crate the new image from this function
createImageFrom(urlStr)
setAnchors()
}
}
func createImageFrom(_ urlStr: String) {
if let cachedImage = imageCache.object(forKey: urlStr as AnyObject) as? UIImage {
// 4. if the image is in cache call this function to show the image
showAllAndSetImageView(with: cachedImage)
} else {
guard let url = URL(string: urlStr) else { return }
// 5. if the image is not in cache start a urlSession and initialize it with the task variable from step 2
task = URLSession.shared.dataTask(with: url,completionHandler: {
[weak self](data,response,error) in
if let error = error { return }
if let response = response as? HTTPURLResponse {
print("response.statusCode: \(response.statusCode)")
guard 200 ..< 300 ~= response.statusCode else { return }
}
guard let data = data,let image = UIImage(data: data) else { return }
// 6. add the image to cache
imageCache.setObject(image,forKey: photoUrlStr as AnyObject)
DispatchQueue.main.async { [weak self] in
// 7. call this function to show the image
self?.showAllAndSetImageView(with: image)
}
})
task?.resume()
}
}
func showAllAndSetImageView(with image: UIImage) {
// 8. resize the image
let resizedImage = resizeImageToCenter(image: image,size: 40) // can also use self.frame.height
imageView.image = resizeImage
showAll()
}
// 9. func to resize the image
func resizeImageToCenter(image: UIImage,size: CGFloat) -> UIImage {
let size = CGSize(width: size,height: size)
// Define rect for thumbnail
let scale = max(size.width/image.size.width,size.height/image.size.height)
let width = image.size.width * scale
let height = image.size.height * scale
let x = (size.width - width) / CGFloat(2)
let y = (size.height - height) / CGFloat(2)
let thumbnailRect = CGRect.init(x: x,y: y,width: width,height: height)
// Generate thumbnail from image
UIGraphicsBeginImageContextWithOptions(size,false,0)
image.draw(in: thumbnailRect)
let thumbnail = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()
return thumbnail!
}
func resetAll() { ... }
func showAll() { ... }
func setAnchors() { ... }