android RecyclerView获得单个Item的ViewHolder

         if (position - firstItemPosition >= 0) {  
             //得到要更新的item的view  
             View view = mRecyclerView.getChildAt(position - firstItemPosition+1);  
             if (null != mRecyclerView.getChildViewHolder(view)){  
                 ProductsViewHolder viewHolder = (ProductsViewHolder)mRecyclerView.getChildViewHolder(view);  
   
 //do something  
            }  ```