DownloadManager通知不显示百分比

Question

我正在尝试使用API​​11 +中的DownloadManager下载文件。到目前为止，文件下载已经很好，但操作栏通知显示未确定大小的进度条，查询轮询返回没有大小，直到文件完全下载。

代码：

DownloadManager.Request request = new DownloadManager.Request(Uri.parse(attachment.getUrl())
            .setAllowedNetworkTypes(
                    DownloadManager.Request.NETWORK_WIFI
                            | DownloadManager.Request.NETWORK_MOBILE)
            .setMimeType(attachment.getContentType())
            .setAllowedOverRoaming(true)
            .setTitle(attachment.getName())
            .setDestinationInExternalPublicDir(Environment.DIRECTORY_DOWNLOADS,
                    attachment.getName())
            .setNotificationVisibility(DownloadManager.Request.VISIBILITY_VISIBLE_NOTIFY_COMPLETED)
            .addRequestHeader("Content-Length", attachment.getSizeInBytes() + "");
long lastDownload = mDownloadManager.enqueue(request);

我的查询是

  double progress = 0.0;
  query.setFilterById(downloadId);
  Cursor cursor = mDownloadManager.query(query);
  if (cursor.moveToFirst()) {
      int sizeIndex = cursor.getColumnIndex(DownloadManager.COLUMN_TOTAL_SIZE_BYTES);
      int downloadedIndex = cursor
              .getColumnIndex(DownloadManager.COLUMN_BYTES_DOWNLOADED_SO_FAR);
      long size = cursor.getInt(sizeIndex);
      long downloaded = cursor.getInt(downloadedIndex);
      Log.e("THINGS", "Downloaded " + downloaded + " of a total of " + size);
      if (size != -1) {
          progress = downloaded * 100.0 / size;
      }
  }

该块中的日志语句返回

        // Downloaded 4127 of a total of -1
        // Downloaded 842903 of a total of -1
        // Downloaded 1440759 of a total of 1440759

，通知与此类似

任何人都可以指出我做错了什么，或者问题是否存在于服务器上？