AVAssetExportSession.requestExportSession回调从未调用过（swift 3，iOS10）

Question

以下代码从不调用导出的回调函数。导出会话创建得很好。我没有看到任何错误，也没有任何进展。 CPU是0％。我没有看到任何例外。状态为1（进行中），进度为0，错误为零。视频在画廊中播放。我可以成功获取该视频的图片。我已经将代码提取到单个UIViewController进行测试，请参阅以下内容：

我使用iOS10.1.1测试了我在iPad上录制的视频。

import UIKit 
import Photos 

class ViewController: UIViewController { 

override func viewDidLoad() { 
    super.viewDidLoad() 
    // Do any additional setup after loading the view, typically from a nib. 
} 

override func didReceiveMemoryWarning() { 
    super.didReceiveMemoryWarning() 
    // Dispose of any resources that can be recreated. 
} 

// MARK: Properties 
@IBOutlet weak var button: UIButton! 

// MARK: Actions 
@IBAction func onPress(_ sender: UIButton) { 
    requestGalleryPermission() { 
     (_ hasPermission: Bool) in 
     if hasPermission { 
      // fetch the asset from Photos 
      let fetchResult = PHAsset.fetchAssets(withLocalIdentifiers: ["9FFAD8B5-0941-4A95-830F-4ACFA563B71B/L0/001"], options: nil) 

      // if we successfully fetched the asset... 
      if let asset = fetchResult.firstObject { 

       self.exportAsset(asset) 
      } 
     } 
    } 
} 

func exportAsset(_ asset: PHAsset) { 
    let tempFilename = "full_sized_image.mov" 
    var tempURL = URL(fileURLWithPath: NSTemporaryDirectory(), isDirectory: true).appendingPathComponent(tempFilename) 
    tempURL = tempURL.standardizedFileURL 


    let options = PHVideoRequestOptions() 
    options.deliveryMode = .highQualityFormat 
    options.isNetworkAccessAllowed = true 

    // remove any existing file at that location 
    do { 
     try FileManager.default.removeItem(at: tempURL) 
    } 
    catch { 
     // most likely, the file didn't exist. Don't sweat it 
    } 

    PHImageManager.default().requestExportSession(forVideo: asset, options: options, exportPreset: AVAssetExportPresetHighestQuality) { 
     (exportSession: AVAssetExportSession?, _) in 

     if exportSession == nil { 
      print("COULD NOT CREATE EXPORT SESSION") 
      return 
     } 

     exportSession!.outputURL = tempURL 
     exportSession!.outputFileType = AVFileTypeQuickTimeMovie 

     print("GOT EXPORT SESSION") 
     exportSession!.exportAsynchronously() { 
      print("COMPLETION HANDLER!!!!") 
     } 

     print("progress: \(exportSession!.progress)") 
     print("error: \(exportSession!.error)") 
     print("status: \(exportSession!.status.rawValue)") 
    } 
} 

func requestGalleryPermission(_ completionHandler: @escaping (_ hasPermission: Bool) -> Void) { 

    let authorizationStatus = PHPhotoLibrary.authorizationStatus() 
    if authorizationStatus == .denied || authorizationStatus == .restricted { 
     completionHandler(false) 
    } 
    else if authorizationStatus == .authorized { 
     completionHandler(true) 
    } 
    else { 
     // ask for authorization 
     PHPhotoLibrary.requestAuthorization({ (status: PHAuthorizationStatus) in 

      // if the user gave us authorization... 
      if status == .authorized { 

       print("User gave authorization") 

       completionHandler(true) 
      } 
      else { 
       print("User denied authorization") 

       completionHandler(false) 
      } 
     }) 
    } 
} 
} 

Answer 1

斯威夫特3 工作就像我的一个魅力！

func exportVideoAsset(_ asset: PHAsset) { 
    let filename = UUID().uuidString.appending(".mp4") // setting random file name 

    let documentsUrl = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first! 

    do { 
     var fileurl = try documentsUrl.absoluteString.appending(filename).asURL() 
     print("exporting video to ", fileurl) 
     fileurl = fileurl.standardizedFileURL 


     let options = PHVideoRequestOptions() 
     options.deliveryMode = .highQualityFormat 
     options.isNetworkAccessAllowed = true 

     // remove any existing file at that location 
     do { 
      try FileManager.default.removeItem(at: fileurl) 
     } 
     catch { 
      // most likely, the file didn't exist. Don't sweat it 
     } 

     PHImageManager.default().requestExportSession(forVideo: asset, options: options, exportPreset: AVAssetExportPresetHighestQuality) { 
      (exportSession: AVAssetExportSession?, _) in 

      if exportSession == nil { 
       print("COULD NOT CREATE EXPORT SESSION") 
       return 
      } 

      exportSession!.outputURL = fileurl 
      exportSession!.outputFileType = AVFileTypeMPEG4 //file type encode goes here, you can change it for other types 

      print("GOT EXPORT SESSION") 
      exportSession!.exportAsynchronously() { 
       print("EXPORT DONE") 
      } 

      print("progress: \(exportSession!.progress)") 
      print("error: \(exportSession!.error)") 
      print("status: \(exportSession!.status.rawValue)") 
     } 
    } 
    catch { 
     // something may happend here, like no disk space 
    } 
}