code for my app that needs to be fixed

chords.java

//my ChordsListActiviy aka MainActivity
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.view.View;
import android.widget.ImageButton;

import java.io.Serializable;
import java.util.ArrayList;
import java.util.List;

public class ChordsListActivity extends Activity implements View.OnClickListener{
    private RecyclerView chordsList;
    private RecyclerView.LayoutManager listLayoutManager;
    private List<Accordo> chords = new ArrayList<Accordo>();
    private Accordo accordo;

    private ArrayList<Accordo> getChords() {
        ArrayList<Accordo> chords = new ArrayList<>();

        Accordo a=new Accordo();
        a.setName("Do maggiore");
        a.setNote("Do, Mi, Sol");
        a.setImage(R.drawable.do_maggiore);
        chords.add(a);

        a=new Accordo();
        a.setName("do 5");
        a.setNote("na, na, na");
        a.setImage(R.drawable.do5);
        chords.add(a);

        a=new Accordo();
        a.setName("do 6");
        a.setNote("na,na,na");
        a.setImage(R.drawable.do6);
        chords.add(a);

        a=new Accordo();
        a.setName("do 7");
        a.setNote("na,na,na");
        a.setImage(R.drawable.do7);
        chords.add(a);

        //many more!!

        return chords;
    }

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_chords_list);

        for(int i=0; i<10; i++) {
            accordo = new Accordo(); // You've added 3 data in your question, while I've added 10 data for sample code.
            accordo.setName("My Name is " + i);
            chords.add(accordo);
        }
        findViewById(R.id.tasto_ricerca).setOnClickListener(this);
        chordsList = (RecyclerView) findViewById(R.id.chords_recycler);

        //use a linear layout manager
        listLayoutManager = new LinearLayoutManager(this);
        chordsList.setLayoutManager(listLayoutManager);

         ChordsListAdapter adapter = new ChordsListAdapter(this, getChords());
        chordsList.setAdapter(adapter);
    }

    @Override
    public void onClick(View view) {
        switch (view.getId()) {
            case R.id.tasto_ricerca:
                Intent intent = new Intent(this, SearchActivity.class);
                intent.putExtra("data", (Serializable) chords);  // This will pass the whole arraylist to search activity
                startActivity(intent);
                break;
        }
    }
}

//My SearchActivity that load when the search_button in the ChordsListActivity is pressed
public class SearchActivity extends Activity {
    SearchView sv;
    private RecyclerView recyclerView;
    private List<Accordo> list;

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.search_layout);

        try {
            list = (List<Accordo>) getIntent().getSerializableExtra("data");  // Here you will get that list using Intent
            Log.e("data===", list.get(0).getNome());
        } catch(Exception e) {
            e.printStackTrace();
        }

        recyclerView = (RecyclerView) findViewById(R.id.lista_ricerca);
        LinearLayoutManager linearLayoutManager = new LinearLayoutManager(this);
        linearLayoutManager.setOrientation(LinearLayoutManager.VERTICAL);
        recyclerView.setLayoutManager(linearLayoutManager);
        recyclerView.setHasFixedSize(true);

        SearchAdapter recyclerViewAdapter = new SearchAdapter(this, list); // Added that arraylist in my recyclerview adapter and that's it....
        recyclerView.setAdapter(recyclerViewAdapter);
    }
}

//My SearchAdapter
public class SearchAdapter extends RecyclerView.Adapter<SearchAdapter.MyViewHolder> {

    private List<Accordo> data = new ArrayList<Accordo>();
    private Context mContext;

    public SearchAdapter(Context ctx, List<Accordo> mData) {
        mContext = ctx;
        data = mData;
    }

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

    @Override
    public void onBindViewHolder(MyViewHolder holder, int position) {
        try {
            if(!data.isEmpty()) {
                holder.tvName.setText(data.get(position).getNome());
            } else {
                holder.tvName.setText("No data available....");
            }
        } catch(Exception e) {
            e.printStackTrace();
        }
    }

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

    //My ViewHolder class
    public class MyViewHolder extends RecyclerView.ViewHolder {

        TextView tvName, tvNote;

        public MyViewHolder(View itemView) {
            super(itemView);

            tvName = (TextView) itemView.findViewById(R.id.ricerca_nome);
        }
    }
}

//My SearchFilter
public class SearchFilter extends Filter{

    SearchAdapter adapter;
    ArrayList<Accordo> filterList;

    public SearchFilter(ArrayList<Accordo> filterList, SearchAdapter adapter) {
        this.adapter=adapter;
        this.filterList=filterList;
    }


    @Override
    protected FilterResults performFiltering(CharSequence constraint) {
        FilterResults results = new FilterResults();

        //CHECK CONSTRAINT VALIDITY
        if(constraint!=null && constraint.length()>0){
            /**CHANGE TO UPPER*/
            constraint=constraint.toString().toUpperCase();
            /**STORE THE FILTERED CHORDS*/
            ArrayList<Accordo> filteredChords = new ArrayList<>();

            for(int i=0; i<filterList.size();i++){
                //CHECK
                if(filterList.get(i).getNome().toUpperCase().contains(constraint))
                    //ADD CHORD TO FILTEREDCHPRDS
                    filteredChords.add(filterList.get(i));
            }

            results.count = filteredChords.size();
            results.values = filteredChords;
        } else {
            results.count = filterList.size(); //0
            results.values = filterList; //null
        }

        return results;
    }

    @Override
    protected void publishResults(CharSequence constraint, FilterResults results) {
    
        /** getting an error here because filterList is not in my adapter class anymore*/
        adapter.filterList = (ArrayList<Accordo>) results.values; 

        //REFRESH
        adapter.notifyDataSetChanged();

    }
}

//and finally my Accordo.class
public class Accordo implements Serializable{
    private String name, note;
    private int image;
    

    /** meodi get e set */
    public String getNome() {return name;}
    public String getNote() {return note;}
    public int getImage() {return image;}

    public void setName(String s) {this.name = s;}
    public void setNote(String n) {this.note = n;}
    public void setImage(int i) {this.image = i;}
}