Android RecyclerView.Adapter onCreateViewHolder() working

Question

I am using RecyclerView.Adapter but I am little confused regarding working of its method onCreateViewHolder.

  @Override
public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup viewGroup, int viewType) {
    if(viewType==TYPE_ITEM) {

        View mView = LayoutInflater.from(viewGroup.getContext()).inflate(R.layout.inflate_common_item, viewGroup, false);
        ViewHolder vh = new ViewHolder(mView);
        return vh;

    } else {
        View mView = LayoutInflater.from(viewGroup.getContext()).inflate(R.layout.inflate_uncommon_item, viewGroup, false);
        ViewHolderFooter vh = new ViewHolderFooter(mView);
        return vh;

    }
}

So incase I have 10 items in my list so for each item this method will be called and every time a new ViewHolder will be created of course it'll one time for each view but now my question is when we were using ListView and BaseAdapter with them we store ViewHolder in tag and use that. We don't create ViewHolder for each item.

 @Override
    public View getView(int position, View convertView, ViewGroup parent) {
            MyViewHolder mViewHolder;

            if(convertView == null) {
                    convertView = inflater.inflate(R.layout.layout_list_item, null);
                    mViewHolder = new MyViewHolder();
                    convertView.setTag(mViewHolder);
            } else {
                    mViewHolder = (MyViewHolder) convertView.getTag();
            }

            mViewHolder.tvTitle = detail(convertView, R.id.tvTitle, myList.get(position).getTitle());
            mViewHolder.tvDesc  = detail(convertView, R.id.tvDesc,  myList.get(position).getDescription());
            mViewHolder.ivIcon  = detail(convertView, R.id.ivIcon,  myList.get(position).getImgResId());

            return convertView;
    }

So are we not creating extra viewholders object. Please help me understand the pros and cons.

Thanks

Answer 1

onCreateViewHolder only creates a new view holder when there are no existing view holders which the RecyclerView can reuse. So, for instance, if your RecyclerView can display 5 items at a time, it will create 5-6 ViewHolders, and then automatically reuse them, each time calling onBindViewHolder.

Its similar to what your code in the ListView does (checking if convertView is null, and if not, grabbing the existing ViewHolder from the tag), except, with RecyclerView, this is all done automatically.

I suppose this is one of the pros with using a RecyclerView - you don't need to worry so much about reusing ViewHolders as you do with ListView. The con is, RecyclerView is very customisable, but has very little built in functionality - unlike ListView which is not very customisable, but has a lot of built in functionality.