int android.support.v7.widget.RecyclerView$ViewHolder.mItemViewType' on a null.....

Android.support.v7.widget.RecyclerView$ViewHolder.mItemViewType' on a null..空指针问题，费劲心思才找到报空指针的原因：

代码是这样的，有多种布局类型

@Override
    public int getItemViewType(int position) {
        BmobIMMessage message = msgs.get(position);
        if(message.getMsgType().equals(BmobIMMessageType.IMAGE.getType())){
            return message.getFromId().equals(currentUid) ? TYPE_SEND_IMAGE: TYPE_RECEIVER_IMAGE;
        }else if(message.getMsgType().equals(BmobIMMessageType.LOCATION.getType())){
            return message.getFromId().equals(currentUid) ? TYPE_SEND_LOCATION: TYPE_RECEIVER_LOCATION;
        }else if(message.getMsgType().equals(BmobIMMessageType.VOICE.getType())){
            return message.getFromId().equals(currentUid) ? TYPE_SEND_VOICE: TYPE_RECEIVER_VOICE;
        }else if(message.getMsgType().equals(BmobIMMessageType.TEXT.getType())){
            return message.getFromId().equals(currentUid) ? TYPE_SEND_TXT: TYPE_RECEIVER_TXT;
        }else if(message.getMsgType().equals(BmobIMMessageType.VIDEO.getType())){
            return message.getFromId().equals(currentUid) ? TYPE_SEND_VIDEO: TYPE_RECEIVER_VIDEO;
        }else if(message.getMsgType().equals("agree")) {//显示欢迎
            return TYPE_AGREE;
        }else{
//            return -1;
            return  TYPE_AGREE;
        }

然后这是

getItemCount()

@Override
public int getItemCount() {
    return msgs.size();

}

最后发现是因为itemCount与viewType不匹配导致的

例如：

recyclerview总共有6种类型，现在只写了一种类型测试，其他的都没有些，才导致报空，然后在getItemCount中return 1;  就ok了