获取保存到照片库的图像的 PHAsset/localIdentifier

Posted 2023-03-08

【中文标题】获取保存到照片库的图像的 PHAsset/localIdentifier

【英文标题】：Get PHAsset/localIdentifier of image saved to photo library

【发布时间】：2021-01-02 23:12:30

【问题描述】：

我正在使用UIImageWriteToSavedPhotosAlbum 将图像保存到“照片”应用。这是我发现的唯一可以让您执行此操作的函数。

这是我的代码：

import UIKit
import Photos

class ViewController: UIViewController 

    /// photo of a cactus
    let photoURL = URL(string: "https://raw.githubusercontent.com/aheze/DeveloperAssets/master/cactus.png")! /// in my app it's actually a local URL, but this also works
    
    func saveToPhotos() 
        DispatchQueue.global().async 
            let data = try? Data(contentsOf: self.photoURL)
            let image = UIImage(data: data!)
            UIImageWriteToSavedPhotosAlbum(image!, self, #selector(self.image(_:didFinishSavingWithError:contextInfo:)), nil)
        
    

    /// called when the image saving is complete
    @objc func image(_ image: UIImage, didFinishSavingWithError error: NSError?, contextInfo: UnsafeRawPointer) 
        print("Finished saving image")
        
        /// how to get localIdentifier of the image?
        let asset = PHAsset() /// obviously this does not work...
        let localIdentifier = asset.localIdentifier
    

图像已成功保存到照片应用。但是，我需要保留对它的引用，最好是它的localIdentifier，这样我以后可以在用户的​​其他照片中找到它。

例如，当我稍后致电fetchAllPhotos 时，我需要一些方法来定位我保存的仙人掌照片。

var allPhotos: PHFetchResult<PHAsset>?

func fetchAllPhotos() 
    let fetchOptions = PHFetchOptions() /// get all of user's photos
    allPhotos = PHAsset.fetchAssets(with: .image, options: fetchOptions)
    
    if let photos = allPhotos 
        photos.enumerateObjects  (asset, index, stop) in


            /// I need to find the image!  
            /// So I need to know its localIdentifier back when I saved it.
            if asset.localIdentifier == "cactus" 
                print("photo has been found")
            
        
    

有什么办法可以做到吗？ UIImageWriteToSavedPhotosAlbum 完成处理程序引用了UIImage，所以也许我可以从中创建一个PHAsset？或者也许我可以在UIImage 的元数据中写一些东西，我不确定。

【问题讨论】：

重构你的技术以使用 PHAssetChangeRequest，网上有很多例子，placeholderForCreatedAsset 会有正确的 localIdentifier。

@PranavKasetti 看起来很有希望。谢谢！

【参考方案1】：

试试这个保存图片的逻辑：

try phphotoLibrary.shared().performChangesAndWait 
    let imgReq = PHAssetChangeRequest.creationRequestForAsset(from: image)
    self.localID = imgReq.placeholderForCreatedAsset.localIdentifier
 

可以通过以下方式获取本地ID：

photos.enumerateObjects  (asset, index, stop) in
    if asset.localIdentifier == self.localID 
        print("photo was found")