视频并不总是导出到相机胶卷：NSFileManager 的 removeItemAtPath 非阻塞？

Posted 2023-03-07

【中文标题】视频并不总是导出到相机胶卷：NSFileManager 的 removeItemAtPath 非阻塞？

【英文标题】：Video not always exported to Camera Roll: NSFileManager's removeItemAtPath non-blocking?

【发布时间】：2015-06-25 18:34:04

【问题描述】：

看了几篇教程like this 并查看了其他代码导出视频，我们仍然无法解决问题。

有时新视频会导出到相机胶卷，有时则不会。我们甚至无法始终如一地重现该问题。

我们可以想象的唯一问题是NSFileManager.defaultManager().removeItemAtPath 是否不是阻塞调用，但没有文档表明它是异步的，因此我们假设情况并非如此。

每次，writeVideoAtPathToSavedPhotosAlbum 闭包内的“已保存视频”println 都会被调用，这表明视频已成功写入相机胶卷，但我们看不到该视频。

关于如何排除故障的建议？

代码：

        // -- Get path
        let fileName = "/editedVideo.mp4"
        let allPaths = NSSearchPathForDirectoriesInDomains(.DocumentDirectory, .UserDomainMask, true)
        let docsPath = allPaths[0] as! NSString
        let exportPath = docsPath.stringByAppendingFormat(fileName)
        let exportUrl = NSURL.fileURLWithPath(exportPath as String)!

        println(exportPath)

        // -- Remove old video?
        if NSFileManager.defaultManager().fileExistsAtPath(exportPath as String) 
            println("Deleting existing file\n")
            NSFileManager.defaultManager().removeItemAtPath(exportPath as String, error: nil)
        

        // -- Create exporter
        let exporter = AVAssetExportSession(asset: mixComposition, presetName: AVAssetExportPresetHighestQuality)
        exporter.videoComposition = mutableComposition
        exporter.outputFileType = AVFileTypeMPEG4
        exporter.outputURL = exportUrl
        exporter.shouldOptimizeForNetworkUse = true

        // -- Export video
        exporter.exportAsynchronouslyWithCompletionHandler(
            self.exportDidFinish(exporter)
        )
    


    func exportDidFinish(exporter: AVAssetExportSession) 
        println("Finished exporting video!")

        // Write out video to photo album
        let assetLibrary = ALAssetsLibrary()
        assetLibrary.writeVideoAtPathToSavedPhotosAlbum(exporter.outputURL, completionBlock: (url: NSURL!, error: NSError!) in
            println("Saved video \(exporter.outputURL)")

            if (error != nil) 
                println("Error saving video")
            
        )
     

【参考方案1】：

一些可能有助于解决您的问题的建议：

检查视频是否有效/与库兼容，如here

if ([library videoAtPathIsCompatibleWithSavedPhotosAlbum:videoURL])

    [library writeVideoAtPathToSavedPhotosAlbum:videoURL
                                completionBlock:^(NSURL *assetURL, NSError *error)
    ];
 

确保传回的资产 url 不为引用 here 的 nil

if(error)
    NSLog(@"Error: Domain = %@, Code = %@", [error domain], [error localizedDescription]);
 else if(assetURL == nil)

    //It's possible for writing to camera roll to fail, without receiving an error message, but assetURL will be nil
    //Happens when disk is (almost) full
    NSLog(@"Error saving to camera roll: no error message, but no url returned");

 else 
    //remove temp file
    NSError *error;
    [[NSFileManager defaultManager] removeItemAtURL:fileURL error:&error];
    if(error)
        NSLog(@"error: %@", [error localizedDescription]);
    

考虑使用 phphotoLibrary 代替导出视频

PHPhotoLibrary.sharedPhotoLibrary().performChanges(
    let assetRequest = PHAssetChangeRequest.creationRequestForAssetFromVideoAtFileURL(videoURL)
    let assetPlaceholder = assetRequest.placeholderForCreatedAsset
,
completionHandler:  success, error in
    // check and handle error
    // do something with your asset local identifier
)

【讨论】：

您好，请问您有没有机会为这个问题提供帮助？ ***.com/questions/34704032/…。谢谢！

非常感谢马克！