Plusieurs question AndroidStudio/Java

package com.example.artur.myapplication.dokkan_battle.dokkan_battle_activity;

import android.content.Intent;
import android.support.v7.widget.RecyclerView;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.TextView;
import android.widget.Toast;

import com.example.artur.myapplication.R;

import java.util.ArrayList;
import java.util.List;


public class DB_Select_Quest_Adapter extends RecyclerView.Adapter<DB_Select_Quest_Adapter.MyViewHolder> {

    private ImageView area;
    private TextView numereo;
    private RecyclerView layout_quest;

    private int positionItem;

/** Message pour CCM: J'utilise ici return 21 et non pas l'array comme j'ai indiquer plus haut car je faisais des tests pour voir si cela fonctionne **/

    @Override
    public int getItemCount() {
        return 21;
    }

    @Override
    public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        LayoutInflater inflater = LayoutInflater.from(parent.getContext());
        View view = inflater.inflate(R.layout.db_quest_recycler_model_layout, parent, false);
        return new MyViewHolder(view);
    }

    @Override
    public void onBindViewHolder(MyViewHolder holder, int position) {
        Log.i("", String.valueOf(position));
        holder.display(position);
    }

    public int getPositionItem() {
        return positionItem;
    }

    public void setPositionItem(int positionItem) {
        this.positionItem = positionItem;
    }


    public class MyViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener {


        public MyViewHolder(final View itemView) {
            super(itemView);
            area = (ImageView)itemView.findViewById(R.id.imageArea);
            numereo = (TextView)itemView.findViewById(R.id.numero);
            numereo.setOnClickListener(this);

        }

        public void display(int position) {
            String pos = String.valueOf(position);
            numereo.setText(pos);
        }

        @Override
        public void onClick(View v) {
            setPositionItem(getAdapterPosition());
            int nbrPosition = getPositionItem();
            Intent intent = new Intent(v.getContext(), DB_Selected_Quest_Activity.class);
            intent.putExtra("nbr", nbrPosition);
            v.getContext().startActivity(intent);
        }
    }
}