In the below example code I have described how to add Header in RecyclerView without using any external library. For that, Firstly, I have created a header.xml layout and here I have added a TextView.

Now see programing In MyAdapter class I have declared constant variable for header and recycler view items. In onCreateViewHolder method I have inflated both header.xml and list_item.xml layout. In onBindViewHolder method I have set text header name. After this, I have used getItemViewType method for set header postion .

Step(1)Created a new header.xml layout-
 

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:card_view="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">


    <TextView
        android:id="@+id/txt_header"
        android:layout_width="match_parent"
        android:layout_height="50dp"
        android:textStyle="bold"
        android:background="@android:color/holo_orange_dark"
        android:gravity="center"
        android:textColor="@android:color/white"
        android:textSize="24dp"/>
</LinearLayout>

Step(2)-MyAdapter class-

public class MyAdapter extends RecyclerView.Adapter<RecyclerView.ViewHolder> {

    private static final int TYPE_HEADER=0;
    private static final int TYPE_ITEM=1;

    ArrayList<Data>datas;
    Context context;

    public MyAdapter(Context context,ArrayList<Data>datas){
        this.context=context;
        this.datas=datas;
    }

    @Override
    public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        if(viewType==TYPE_HEADER){
            View view= LayoutInflater.from(parent.getContext()).inflate(R.layout.header,parent,false);
            return new HeaderViewHolder(view);
        }else if(viewType==TYPE_ITEM){
            View view =LayoutInflater.from(parent.getContext()).inflate(R.layout.list_item,parent,false);
            return new ItemListViewHolder(view);
        }
        return null;
    }
    private Data getItem(int position){
        return  datas.get(position);
    }

    @Override
    public void onBindViewHolder(RecyclerView.ViewHolder holder, final int position) {
        if(holder instanceof HeaderViewHolder){
            HeaderViewHolder headerViewHolder=(HeaderViewHolder)holder;
            headerViewHolder.txtHeader.setText("Header-List");
            headerViewHolder.txtHeader.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    Toast.makeText(context,"You Clicked header",Toast.LENGTH_SHORT).show();
                }
            });
        }else if(holder instanceof ItemListViewHolder){
            Data currentItem =getItem(position-1);
            ItemListViewHolder itemListViewHolder=(ItemListViewHolder)holder;
            itemListViewHolder.txtName.setText(currentItem.getName());
            itemListViewHolder.txtName.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    Toast.makeText(context,"Clicked item"+(position-1),Toast.LENGTH_SHORT).show();
                }
            });
        }
    }


          @Override
          public  int getItemViewType(int postion){
              if(positionHeader(postion)){
                  return TYPE_HEADER;
              }
              return TYPE_ITEM;
          }
         private boolean positionHeader(int position){
           return position ==0;
          }

 public class HeaderViewHolder extends RecyclerView.ViewHolder{
        TextView txtHeader;
        public HeaderViewHolder (View itemView){
        super(itemView);
        this.txtHeader=(TextView)itemView.findViewById(R.id.txt_header);

      }
   }
       public class ItemListViewHolder extends RecyclerView.ViewHolder{
         TextView txtName;
         public ItemListViewHolder(View itemView) {
             super(itemView);
            this.txtName=(TextView)itemView.findViewById(R.id.txt_name);
        }
    }

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