ios - 下载视频并将其保存到相机胶卷

Question

根据我阅读的所有示例和文档，这似乎应该是非常简单的事情，但由于某些奇怪的原因我仍然无法让它工作。

我正在使用 Alamofire Frame 工作从 Instagram 下载视频。下载后，我想将视频保存到相机胶卷。这是我下载视频并保存到磁盘的代码:

let destination: (NSURL, NSHTTPURLResponse) -> (NSURL) = {
            (temporaryURL, response) in

            if let directoryURL = NSFileManager.defaultManager().URLsForDirectory(.DocumentDirectory, inDomains: .UserDomainMask)[0] as? NSURL {

                let finalPath = directoryURL.URLByAppendingPathComponent("\(Scripts.dateToString2(date: NSDate())).\(response.suggestedFilename!)")
                InstagramEngine.downloadMediaPath = finalPath

                Scripts.log("Final Path >> \(finalPath)")

                return finalPath
            }

            return temporaryURL
        }

        let request = Alamofire.download(.GET, self.videoURL, destination)

        request.response { _, response, data, error in

                NSNotificationCenter.defaultCenter().postNotificationName(kMediaDownloadComplete, object: nil)

        }

一旦下载完成，就会触发调用此函数将其保存到相机胶卷的通知:

UISaveVideoAtPathToSavedPhotosAlbum(InstagramEngine.downloadMediaPath.URLString, self, Selector("video:didFinishSavingWithError:contextInfo:"), nil)

一切都是根据我的日志语句调用的，没有发生错误。甚至为 UISaveVideoAtPathToSavedPhotosAlbum 成功调用了 didFinishSavingWithError，我确认没有发现错误。但是当我去查看相机胶卷时，我仍然没有看到那里保存的视频。有什么想法吗？

Answer 1

不幸的是，存在与 UISaveVideoAtPathToSavedPhotosAlbum 和 mp4 格式相关的错误，这是 Instagram 使用的格式。

有一个名为 UIVideoAtPathIsCompatibleWithSavedPhotosAlbum 的辅助方法可以帮助指示视频是否与方法 UISaveVideoAtPathToSavedPhotosAlbum 兼容。对于从 Instagram 下载的视频，这将返回 false。

---

幸运的是，仍然可以将视频存储到相机胶卷中。这可以使用 ALAssetsLibrary。我已尝试获取您的示例代码并对其进行调整以使用 ALAssetsLibrary，希望这可以帮助您使其正常工作。

import AssetsLibrary

...
...

func downloadVideoToCameraRoll() {

    // Local variable pointing to the local file path for the downloaded video
    var localFileUrl: String?

    // A closure for generating the local file path for the downloaded video. This will be pointing to the Documents directory with a unique UDID file name.
    let destination: (NSURL, NSHTTPURLResponse) -> (NSURL) = {
        (temporaryURL, response) in

        if let directoryURL = NSFileManager.defaultManager().URLsForDirectory(.DocumentDirectory, inDomains: .UserDomainMask)[0] as? NSURL {
            let finalPath = directoryURL.URLByAppendingPathComponent("\(NSUUID()).\(response.suggestedFilename!)")
            localFileUrl = finalPath.absoluteString
            return finalPath
        }

        return temporaryURL
    }

    // The media post which should be downloaded
    let postURL = NSURL(string: "https://api.instagram.com/v1/media/" + "952201134785549382_250131908" + "?access_token=" + InstagramEngine.sharedEngine().accessToken)!

    // Then some magic happens that turns the postURL into the videoURL, which is the actual url of the video media:
    let videoURL = NSURL(string: "https://scontent.cdninstagram.com/hphotos-xfp1/t50.2886-16/11104555_1603400416544760_416259564_s.mp4")!

    // Download starts
    let request = Alamofire.download(.GET, videoURL, destination)

    // Completion handler for the download
    request.response { (request, response, data, error) -> Void in
        if let path = localFileUrl {
            let isVideoCompatible = UIVideoAtPathIsCompatibleWithSavedPhotosAlbum(path)
            println("bool: \(isVideoCompatible)") // This logs out "bool: false"

            let library = ALAssetsLibrary()

            library.writeVideoAtPathToSavedPhotosAlbum(NSURL(string: path), completionBlock: { (url, error) -> Void in
                // Done! Go check your camera roll
            })
        }
    }
}