Edit a contact within this calendar

I'm trying to edit a contact within this calendar. But when you save the edit it creates a new one.

public class MainActivity extends AppCompatActivity {
    public static final String CONTATO = "contato";
    public static final int REQUEST_NOVO = 1;
    private ListView listaV;
    private List<Contato> lista = new ArrayList<>();
    private AdapterContato adapter;
private ContatoDAO dao;
private Contato contatoselecionado;
private static Bitmap imagem;

public static Bitmap getImagem() {
    return imagem;

}


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

}
private void atualizacao(){

    dao = new ContatoDAO(this);
    lista = dao.getLista();
    dao.close();
}

@Override
public void onCreateContextMenu(ContextMenu menu, View v, ContextMenu.ContextMenuInfo menuInfo) {
    MenuItem editar = menu.add("Editar");
    editar.setOnMenuItemClickListener(new MenuItem.OnMenuItemClickListener() {
        @Override
        public boolean onMenuItemClick(MenuItem menuItem) {
            Intent intent = new Intent(MainActivity.this,NovoActivity.class);
            intent.putExtra(CONTATO, contatoselecionado);
            startActivity(intent);
            return false;
        }
    });
}



@Override
public boolean onCreateOptionsMenu(Menu menu) {
    MenuInflater inflater = getMenuInflater();
    inflater.inflate(R.menu.menu, menu);
    return true;}




public void novo(MenuItem item) {
    Intent intent = new Intent(this, NovoActivity.class);
    startActivityForResult(intent, REQUEST_NOVO);
}
@Override
protected void onResume() {
    super.onResume();
    listaV = findViewById(R.id.Contatos);
    adapter = new AdapterContato(this, lista);
    listaV.setAdapter(adapter);
    atualizacao();


    listaV.setOnItemClickListener(new AdapterView.OnItemClickListener() {
        @Override
        public void onItemClick(AdapterView<?> adapterView, View view, int posicao, long l) {
            contatoselecionado = (Contato) adapterView.getItemAtPosition(posicao);

            Intent itent = new Intent(MainActivity.this, DetalheActivity.class);
            itent.putExtra(CONTATO,contatoselecionado);
            startActivity(itent);

        }
    });

    listaV.setOnItemLongClickListener(new AdapterView.OnItemLongClickListener() {
        @Override
        public boolean onItemLongClick(AdapterView<?> adapterView, View view, int posicao, long l) {
            contatoselecionado = (Contato) adapterView.getItemAtPosition(posicao);


            return false;


        }
    });

    registerForContextMenu(listaV);



}

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    if(requestCode == REQUEST_NOVO){
        switch(resultCode){
            case RESULT_OK:
               /*
                Contato contato = (Contato) data.getSerializableExtra(MainActivity.CONTATO);
                contato.setImagem(NovoActivity.getimagem());
                */
                atualizacao();
             adapter.notifyDataSetChanged();
             break;

            case RESULT_CANCELED:
                Toast.makeText(this,"Cancelado.", Toast.LENGTH_LONG).show();
                break;
        }

    }}
}