有时候为了只让有权限的用户下载，不能直接把文件放在硬盘上以静态文件的方式直接提供下载，下面这段代码实现通过文件流的方式下载：

  def download_android(request):
     
      your_file_path = '/xxx/xxx/'
      original_filename = 'xxx.xx'
      file_path = your_file_path + original_filename
     
      fp = open(file_path, 'rb')
      response = HttpResponse(fp.read())
      fp.close()
      type, encoding = mimetypes.guess_type(original_filename)
      if type is None:
          type = 'application/octet-stream'
      response['Content-Type'] = type
      response['Content-Length'] = str(os.stat(file_path).st_size)
      if encoding is not None:
          response['Content-Encoding'] = encoding

      # To inspect details for the below code, see http://greenbytes.de/tech/tc2231/
      if u'WebKit' in request.META['HTTP_USER_AGENT']:
          # Safari 3.0 and Chrome 2.0 accepts UTF-8 encoded string directly.
          filename_header = 'filename=%s' % original_filename.encode('utf-8')
      elif u'MSIE' in request.META['HTTP_USER_AGENT']:
          # IE does not support internationalized filename at all.
          # It can only recognize internationalized URL, so we do the trick via routing rules.
          filename_header = 'filename=%s' % original_filename.encode('utf-8')
      else:
          # For others like Firefox, we follow RFC2231 (encoding extension in HTTP headers).
          filename_header = 'filename*=UTF-8\'\'%s' % urllib.quote(original_filename.encode('utf-8'))
      response['Content-Disposition'] = 'attachment; ' + filename_header
      return response