/**
  * 删除一个任务
  *
  * @param downloadId
  */
 public void deleteTask(int downloadId) {
   if (mDbController.deleteTask(downloadId)) {
     FileDownloaderModel model = getFileDownloaderModelById(downloadId);
     if (model != null) { // 删除文件
       new File(model.getPath()).delete();
     }
     pauseTask(downloadId);
     removeDownloadingTask(downloadId);
     removeWaitQueueTask(downloadId);
     try {
       mAllTasks.remove(downloadId);
     } catch (Exception e) {
       ILogger.e(e);
     }
   } else {
     ILogger.e("delete failure");
   }
 }