通过iOS swift照片框架保存时如何命名照片

Question

我正在使用Xcode 6.3 swift（我认为是 1.2 版）。我的应用程序从网络上的自定义服务器下载照片。然后我希望它将具有给定文件名的照片保存到通过照片框架创建的自定义相册中。我需要能够控制照片/文件名，因为我会跟踪我在数据库中下载了哪些照片，然后需要按名称查看它们。

我创建了一个自定义 PhotoAlbum 类，我试图将与相册交互的所有逻辑包装在其中。下载照片后，我可以调用以下代码，它可以创建相册并保存照片，但正如您将在 savePhoto() 方法中注意到的那样，我不知道保存时在哪里/如何使用 photoName 变量来命名照片。最后，我还需要知道如何在loadPhoto() 方法中按名称检索照片。

感谢您能给我的任何帮助/建议。

let myAlbum = PhotoAlbum("MyAlbum") 

myAlbum.savePhoto(downloadedPhoto, 12)

class PhotoAlbum {

var albumName: String = ""
var albumExists: Bool = false
var assetCollection: PHAssetCollection!
var photosAsset: PHFetchResult!

init(albumName: String) {
    self.albumName = albumName
    self.initializeAlbum()
}

private func initializeAlbum() {

    let fetchOptions = PHFetchOptions()
    fetchOptions.predicate = NSPredicate(format: "title = %@", self.albumName)
    let collection: PHFetchResult = PHAssetCollection.fetchAssetCollectionsWithType(.Album, subtype: .Any, options: fetchOptions)

    if let firstObject: AnyObject = collection.firstObject {
        self.albumExists = true
        self.assetCollection = collection.firstObject as! PHAssetCollection
        if let ac = self.assetCollection {
            self.photosAsset = PHAsset.fetchAssetsInAssetCollection(self.assetCollection, options: nil)
        }
        println("\(self.albumName) album exists")
    }
    else {
        var albumPlaceHolder: PHObjectPlaceholder!

        PHPhotoLibrary.sharedPhotoLibrary().performChanges({

            let request = PHAssetCollectionChangeRequest.creationRequestForAssetCollectionWithTitle(self.albumName)
            albumPlaceHolder = request.placeholderForCreatedAssetCollection

        }, completionHandler: { (success: Bool, error: NSError!) in

            self.albumExists = success
            if success {
                let collection = PHAssetCollection.fetchAssetCollectionsWithLocalIdentifiers([albumPlaceHolder.localIdentifier], options: nil)
                self.assetCollection = collection.firstObject as! PHAssetCollection
                if let ac = self.assetCollection {
                    self.photosAsset = PHAsset.fetchAssetsInAssetCollection(self.assetCollection, options: nil)
                }
                println("\(self.albumName) album made")
            }
            else {
                println("Failed to create \(self.albumName) Album!!!!!!")
            }

        })
    }

}


func savePhoto(image: UIImage, photoID: Int) {
    let photoName = String(photoID)+".jpg"

    PHPhotoLibrary.sharedPhotoLibrary().performChanges({
        let assetRequest = PHAssetChangeRequest.creationRequestForAssetFromImage(image)
        let assetPlaceholder = assetRequest.placeholderForCreatedAsset
        let albumChangeRequest = PHAssetCollectionChangeRequest(forAssetCollection: self.assetCollection, assets: self.photosAsset)
        albumChangeRequest.addAssets([assetPlaceholder])
        }, completionHandler: { (success: Bool, error: NSError!) in

            print(success ? "image added" : "failed to add image")

    })
}

func loadPhoto(photoID: Int64) -> UIImage {
    let photoName = String(photoID)+".jpg"

    return UIImage(named: "no_photo")!
}

func renameAlbum(newAlbumName: String) {
    // need to create the new album and move all photos to that album then remove the old album

}

func reloadPhotos() {
    if let ac = self.assetCollection {
        self.photosAsset = PHAsset.fetchAssetsInAssetCollection(self.assetCollection, options: nil)
    }
}

Answer 1

您需要记下正在创建的资产的localIdentifier 属性，而不是“命名”文件。 localIdentifier 是一个持久标识符（即，它将是跨重启/重新加载的资产的一致 ID）。

我拼凑了一些基本代码，您可以在保存图像时使用它们来获取localIdentifier，并通过localIdentifier 检索和图像。希望这会让您继续前进。

import UIKit
import Photos

class MRPhotosHelper {

    var manager = PHImageManager.defaultManager()

    func saveImageAsAsset(image: UIImage, completion: (localIdentifier:String?) -> Void) {

        var imageIdentifier: String?

        PHPhotoLibrary.sharedPhotoLibrary().performChanges({ () -> Void in
            let changeRequest = PHAssetChangeRequest.creationRequestForAssetFromImage(image)
            let placeHolder = changeRequest.placeholderForCreatedAsset
            imageIdentifier = placeHolder.localIdentifier
        }, completionHandler: { (success, error) -> Void in
            if success {
                completion(localIdentifier: imageIdentifier)
            } else {
                completion(localIdentifier: nil)
            }
        })
    }

    func retrieveImageWithIdentifer(localIdentifier:String, completion: (image:UIImage?) -> Void) {
        let fetchOptions = PHFetchOptions()
        fetchOptions.predicate = NSPredicate(format: "mediaType == %d", PHAssetMediaType.Image.rawValue)
        let fetchResults = PHAsset.fetchAssetsWithLocalIdentifiers([localIdentifier], options: fetchOptions)

        if fetchResults.count > 0 {
            if let imageAsset = fetchResults.objectAtIndex(0) as? PHAsset {
                let requestOptions = PHImageRequestOptions()
                requestOptions.deliveryMode = .HighQualityFormat
                manager.requestImageForAsset(imageAsset, targetSize: PHImageManagerMaximumSize, contentMode: .AspectFill, options: requestOptions, resultHandler: { (image, info) -> Void in
                    completion(image: image)
                })
            } else {
                completion(image: nil)
            }
        } else {
            completion(image: nil)
        }
    }
}

然后你可以这样做：

    // get a reference to our helper
    let helper = MRPhotosHelper()

    // a var to store the localIdentifier for the image we save
    var identifier:String?

    // save the image to library
    if let imageToSave = UIImage(named: "SomeImageName"){
        helper.saveImageAsAsset(imageToSave, completion: { (localIdentifier) -> Void in
            identifier = localIdentifier
        })
    }

    // other stuff

    // retrieve image from library at later date
    if let identifier = identifier {
        helper.retrieveImageWithIdentifer(identifier, completion: { (image) -> Void in
            let retrievedImage = image
        })
    }

在使用更新 UI 之前，您可能需要检查您是否回到了完成闭包中的主线程。