NSURLSessionConfiguration backgroundSessionConfigurationWithIdentifier : Download stops after the app is pushed into background

This method sets the background object.

- (void) downloadWithURL: (NSMutableArray *)urlArray
             pathArr: (NSMutableArray *)pathArr
           mediaInfo: (MediaInfo *)mInfo
{
    bgDownloadMediaInfo = mInfo;
    reqUrlCount = urlArray.count;
    dict = [NSDictionary dictionaryWithObjects:pathArr
                                   forKeys:urlArray];
    mutableDictionary = [dict mutableCopy];
    backgroundConfigurationObject = [NSURLSessionConfiguration backgroundSessionConfigurationWithIdentifier:@"XXXXX"];
    backgroundConfigurationObject.sessionSendsLaunchEvents = YES;
    backgroundConfigurationObject.discretionary = YES;
    backgroundSession = [NSURLSession sessionWithConfiguration: backgroundConfigurationObject
                                                  delegate: self delegateQueue: [NSOperationQueue currentQueue]];
    self.requestUrl = [urlArray objectAtIndex:0];
    download = [backgroundSession downloadTaskWithURL:self.requestUrl];
    [download resume];

}

These are the completion handlers.

#pragma Mark - NSURLSessionDownloadDelegate

- (void)URLSession: (NSURLSession *)session
      downloadTask: (NSURLSessionDownloadTask *)downloadTask
didFinishDownloadingToURL: (NSURL *)location
{
  LogDebug(@"Download complete for request url (%@)", downloadTask.currentRequest.URL);
  NSString *temp = [mutableDictionary objectForKey:downloadTask.currentRequest.URL];
  NSString *localPath = [NSString stringWithFormat: @"%@",temp];
  NSFileManager *fileManager = [NSFileManager defaultManager];
  NSURL *destinationURL = [NSURL fileURLWithPath: localPath];
  NSError *error = nil;
  [fileManager moveItemAtURL:location toURL:destinationURL error:&error];
  LogDebug(@"Moving download file at url : (%@) to : (%@)", downloadTask.currentRequest.URL, destinationURL);
  reqUrlCount --;
  downloadSegment ++;
  // Handover remaining download requests to the OS
  if ([finalUrlArr count] != 0) {
    // remove the request from the array that got downloaded.
    [finalUrlArr removeObjectAtIndex:0];
    [finalPathArr removeObjectAtIndex:0];
    if ([finalUrlArr count] > 0) {
      // proceed with the next request on top.
      self.requestUrl = [finalUrlArr objectAtIndex:0];
      download = [backgroundSession downloadTaskWithURL:self.requestUrl];
      [download resume];
    }
  }
  if ([adsArray count] > 0) {
    adsArrayCount --;
    // delegate back once all the ADs segments have been downloaded.
    if (adsArrayCount == 0) {
      for (int i = 0; i < [adsArray count]; i++) {
        NSArray *ads = [adsArray objectAtIndex: i];
        for (int j = 0; j < [ads count]; j++) {
          MediaInfo *ad = [ads objectAtIndex: j];
          [self setDownloadComplete: ad];
          // skip sending downloadFinish delegate if the media is marked as downloadDone
          if (!ad.downloadDone) {
            [delegate MediaDownloadDidFinish: ad.mediaId error: NO];
          }
          ad.downloadDone = YES;
        }
      }
      downloadSegment = 0;
    }
  }

  // delegate back once all the main media segments have been downloaded.
  if (reqUrlCount == 0) {
    [self setDownloadComplete: mediaInfo];
    state = DownloadState_Done;
    // skip sending downloadFinish delegate if the media is marked as downloadDone
    if (!bgDownloadMediaInfo.downloadDone) {
      [delegate MediaDownloadDidFinish: bgDownloadMediaInfo.mediaId error: NO];
    }
    bgDownloadMediaInfo.downloadDone = YES;
    [urlArr release];
    [pathArr release];
    [finalUrlArr release];
    [finalPathArr release];
    // invalidate the NSURL session once complete
    [backgroundSession invalidateAndCancel];
  }
}



- (void)URLSession: (NSURLSession *)session
              task: (NSURLSessionTask *)task
didCompleteWithError: (NSError *)error
{
  if (error) {
    NSLog(@"Failure to download request url (%@) with error (%@)", task.originalRequest.URL, error);
  }
}

- (void)URLSession:(NSURLSession *)session
      downloadTask:(NSURLSessionDownloadTask *)downloadTask
      didWriteData:(int64_t)bytesWritten
 totalBytesWritten:(int64_t)totalBytesWritten
totalBytesExpectedToWrite:(int64_t)totalBytesExpectedToWrite
{
  // save the total downloaded size
  [self downloaderDidReceiveData:bytesWritten];
  // enable the log only for debugging purpose.
  // LogDebug(@"totalBytesExpectedToWrite %llu, totalBytesWritten %llu, %@", totalBytesExpectedToWrite, totalBytesWritten, downloadTask.currentRequest.URL);
}

With out this code(beginBackgroundTaskWithExpirationHandler) the download stops when the app is pushed into background.

//  AppDelegate_Phone.m
- (void)applicationDidEnterBackground: (UIApplication *)application
{
    NSLog(@"applicationDidEnterBackground");
    UIApplication  *app = [UIApplication sharedApplication];
    UIBackgroundTaskIdentifier bgTask;

    bgTask = [app beginBackgroundTaskWithExpirationHandler:^{
        [app endBackgroundTask:bgTask];
    }];
}