ios - 使用 Photos 框架进行内存管理

Question

我在从 iOS 中的照片框架检索对象时遇到内存问题。我给你看我的代码:

public class func randomImageFromLibrary(
        completion: @escaping (_ error: ImageProviderError?, _ image: UIImage?, _ creationDate: Date?, _ location: CLLocation?) -> Void) {

        // Create the fetch options sorting assets by creation date
        let fetchOptions = PHFetchOptions.init()
        fetchOptions.sortDescriptors = [ NSSortDescriptor.init(key: "creationDate", ascending: true) ]
        fetchOptions.predicate = NSPredicate.init(format: "mediaType == \(PHAssetMediaType.image)")

        DispatchQueue.global(qos: .userInitiated).async {

            let fetchResult = PHAsset.fetchAssets(with: PHAssetMediaType.image, options: nil)

            if fetchResult.count == 0 {

                // The restoreAnimationAfterFetching method contains UI changes, this is why
                // we perform this code on the main thread
                Async.main({

                    print("No photos in the library!")

                    completion(.PhotoLibraryEmpty, nil, nil, nil)
                })

                return
            }

            var photos: [PHAsset] = []

            // Enumerate the PHAssets present in the array and move everything to the photos array
            fetchResult.enumerateObjects({ (object: PHAsset, index, stop: UnsafeMutablePointer<ObjCBool>) in
                //let asset = object
                photos.append(object)
            })


            let asset = photos[0] // This could be any number, 0 is only a test

            // The options for the image request
            // We want the HQ image, current version (edited or not), async and with the possibility to access the network
            let options = PHImageRequestOptions.init()
            options.deliveryMode = PHImageRequestOptionsDeliveryMode.highQualityFormat
            options.version = PHImageRequestOptionsVersion.current
            options.isSynchronous = false
            options.isNetworkAccessAllowed = true

            PHImageManager.default().requestImageData(
                for: asset,
                options: options,
                resultHandler: { (imageData: Data?, dataUTI: String?, orientation: UIImageOrientation, info: [AnyHashable : Any]?) in

                    // If the image data is not nil, set it into the image view
                    if (imageData != nil) {

                        Async.main({

                            // Get image from the imageData
                            let image = UIImage.init(data: imageData!)

                            completion(nil, image, asset.creationDate, asset.location)
                        })
                    } else {

                        // TODO: Error retrieving the image. Show alert
                        print("There was an error retrieving the image! \n\(info![PHImageErrorKey])")

                        completion(.GenericError, nil, nil, nil)
                    }
                }
            )
            }
        }

Async是一个可以轻松管理 GCD 的框架。当我调用此方法时，我的内存负载很重。如果我多次调用它，我可以在 Instruments 中看到 PHAsset 在不释放任何东西的情况下继续增加。我想到了 autoreleasepool，但我不确定如何正确使用它。你有什么建议或类似的东西吗？最后一件事是，即使在由于内存负载过重而不断崩溃的 Today Widget 中，我也需要使用它。

Answer 1

请注意，您正在使用异步调用 requestImageData 的选项:

isSynchronous = false

您可能不需要，因为调用代码已经在后台线程中。

这也意味着结果处理程序可能会被多次调用。结合 isNetworkAccessAllowed 选项可能会延迟请求的完成和 PHAsset 实例的释放。

尝试:

isSynchronous = true
isNetworkAccessAllowed = false