code: DownloadState query(Uri uri) {
      synchronized (currentRequests) {
        for (DownloadRequest request : currentRequests) {
          if (request.uri().toString().equals(uri.toString())) {
            return request.downloadState();
          }
        }
      }
  
      return DownloadState.INVALID;
    }
docs: To check if the request is downloading according to download url.
  
  @param uri the uri to check
  @return true if the request is downloading, otherwise return false