/**
  * 注册Tip类型消息项展示ViewHolder
  *
  * @param viewHolder Tip消息ViewHolder
  */
 public static void registerTipMsgViewHolder(Class<? extends MsgViewHolderBase> viewHolder) {
   MsgViewHolderFactory.registerTipMsgViewHolder(viewHolder);
 }
 /**
  * 根据消息附件类型注册对应的消息项展示ViewHolder
  *
  * @param attach 附件类型
  * @param viewHolder 消息ViewHolder
  */
 public static void registerMsgItemViewHolder(
     Class<? extends MsgAttachment> attach, Class<? extends MsgViewHolderBase> viewHolder) {
   MsgViewHolderFactory.register(attach, viewHolder);
 }