使用Photos框架進行內存管理

Question

我在從iOS中的Photos框架中檢索對象時遇到內存問題。 我告訴你我的代碼：

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是一個輕松管理GCD的框架。 當我調用這個方法時，我的內存負載很重。 如果我多次調用它，我可以看到儀器中的PHAsset繼續增加而不釋放任何東西。 我想過autoreleasepool ，但我不確定如何正確使用它。 你有任何建議或類似的東西嗎？ 最后一件事是我需要在今天的Widget中使用它，因為內存負荷過重而不斷崩潰。

Answer 1

請注意，您正在使用該選項異步調用requestImageData：

isSynchronous = false

您可能不需要，因為調用代碼已經在后台線程中。

這也意味着可以多次調用結果處理程序。 並且與isNetworkAccessAllowed選項結合使用可能會延遲請求的完成和PHAsset實例的釋放。

試試：

isSynchronous = true
isNetworkAccessAllowed = false