code: public AVFile getAVFile() {
      if (actualFile != null) {
        return actualFile;
      } else if (null != file && file.containsKey(FILE_URL)) {
        Map<String, Object> avfileMeta = null;
        if (file.containsKey(FILE_META)) {
          avfileMeta = (Map) file.get(FILE_META);
        }
        AVFile avfile = new AVFile(null, (String) file.get(FILE_URL), avfileMeta);
        if (file.containsKey(OBJECT_ID)) {
          avfile.setObjectId((String) file.get(OBJECT_ID));
        }
        return avfile;
      }
      return null;
    }
docs: 获取文件消息中得AVFile对象
  
  @return