/**
  * 删除一条记录
  *
  * @param
  */
 public void deleteMessage(String key) {
   try {
     db.delete(db.getConnection(), MESSAGE_DB, RECEIVE_TIME + "=?", new String[] {key});
   } catch (Exception e) {
     e.printStackTrace();
   } finally {
     if (db.getConnection().isOpen()) {
       db.closeConnection(db.getConnection());
     }
   }
 }