Question

您好我正在创建一个相册应用程序作为学习项目，我遇到了PHPhotoLibrary.shared().performChangesAndWait的一些问题;主要问题是当方法saveImage具有PHPhotoLibrary.shared().performChangesAndWait代码时;该方法在PHPhotoLibrary.shared().performChangesAndWait完成保存图像之前退出。似乎代码异步执行，即使我使用performChangesAndWait方法，根据文档说它应该等到它完成。

以下是我班级中saveImage方法的代码：

func saveImage(_ image: UIImage) ->Bool {
    print("Executing saveImage")
    var result:Bool = false
    if assetCollection == nil {
        print("the album is nil")
        return result
    }
    print("saveImage: we will start saving the image")
    //TODO: the return false is happening before the photo is save.
    do
    {
        try PHPhotoLibrary.shared().performChangesAndWait({
            let assetChangeRequest = PHAssetChangeRequest.creationRequestForAsset(from: image)
            let assetPlaceHolder = assetChangeRequest.placeholderForCreatedAsset
            let albumChangeRequest = PHAssetCollectionChangeRequest(for: self.assetCollection)
            let enumeration: NSArray = [assetPlaceHolder!]
            albumChangeRequest!.addAssets(enumeration)
            print("saveImage: image was save without issues")
            result = true
            print("saveImage: result value after saving the image: \(result)")
        })
    }
    catch let error
    {
        result = false
        print("saveImage: there was a problem: \(error.localizedDescription)")
    }


    print("saveImage: result value before exiting the method: \(result)")
    return result

}

基本上，当应用程序第一次运行时，返回结果将在保存图像块完成之前执行。

有什么方法可以强制saveImage方法实际等到performChangesAndWait方法实际完成？

提前感谢您的帮助。

Answer 1

这是解决方案（快速5）：

@objc private func handleSavePhoto() {

    guard let previewImage = self.photoImageView.image else { return }

    PHPhotoLibrary.requestAuthorization { (status) in
        if status == .authorized {
            do {
                try PHPhotoLibrary.shared().performChangesAndWait {
                    PHAssetChangeRequest.creationRequestForAsset(from: previewImage)
                }
            } catch let error {
                print("failed to save photo in library: ", error)
            }
        } else {
            print("Something went wrong with permission...")
        }
    }
}

第一次运行时，在自定义相册中保存照片失败

1 个答案: