ios - 如何将图片保存到自定义相册？

Question

我有一个全新的 iOS 应用程序，它可以生成图像并让用户将它们保存到 Camera SavedPhotosAlbum 中。但是，我想做一些类似 Snapchat 和 Frontback 的东西，并将这些图像也保存到自定义命名的相册中。

所以这是我现在的代码:

let imageToSave = self.currentPreviewImage

let softwareContext = CIContext(options:[kCIContextUseSoftwareRenderer: true])
let cgimg = softwareContext.createCGImage(imageToSave, fromRect:imageToSave.extent())

ALAssetsLibrary().writeImageToSavedPhotosAlbum(cgimg, metadata:imageToSave.properties(), completionBlock:nil)

我见过一些人在 Objective-C 中这样做的例子，但我无法将其转换为 Swift，而且我检查了 writeImageToSavedPhotosAlbum 方法签名，但它们似乎都不允许保存到自定义相册。

Answer 1

我想出了这个单例类来处理它:

import Photos

class CustomPhotoAlbum {

    static let albumName = "Flashpod"
    static let sharedInstance = CustomPhotoAlbum()

    var assetCollection: PHAssetCollection!

    init() {

        func fetchAssetCollectionForAlbum() -> PHAssetCollection! {

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

            if let firstObject: AnyObject = collection.firstObject {
                return collection.firstObject as! PHAssetCollection
            }

            return nil
        }

        if let assetCollection = fetchAssetCollectionForAlbum() {
            self.assetCollection = assetCollection
            return
        }

        PHPhotoLibrary.sharedPhotoLibrary().performChanges({
            PHAssetCollectionChangeRequest.creationRequestForAssetCollectionWithTitle(CustomPhotoAlbum.albumName)
        }) { success, _ in
            if success {
                self.assetCollection = fetchAssetCollectionForAlbum()
            }
        }
    }

    func saveImage(image: UIImage) {

        if assetCollection == nil {
            return   // If there was an error upstream, skip the save.
        }

        PHPhotoLibrary.sharedPhotoLibrary().performChanges({
            let assetChangeRequest = PHAssetChangeRequest.creationRequestForAssetFromImage(image)
            let assetPlaceholder = assetChangeRequest.placeholderForCreatedAsset
            let albumChangeRequest = PHAssetCollectionChangeRequest(forAssetCollection: self.assetCollection)
            albumChangeRequest.addAssets([assetPlaceholder])
        }, completionHandler: nil)
    }


}

当您第一次实例化该类时，如果自定义相册尚​​不存在，则会创建它。您可以像这样保存图像:

CustomPhotoAlbum.sharedInstance.saveImage(image)

注意:CustomPhotoAlbum 类假定该应用程序已具有访问照片库的权限。处理权限有点超出了这个问题/答案的范围。所以确保 PHPhotoLibrary.authorizationStatus() == .Authorize 在你使用它之前。并在必要时申请授权。