Não consigo exibir dados sqlite na recyclerview

Estou tentando fazer um aplicativo de agenda telefonica. Ao adicionar o contato no sqlite o programa troca a activity e não exibe os dados cadastrados. O código da Main é:

package com.example.agendatrabdois.UI;

import android.content.Intent;
import android.os.Bundle;

import com.example.agendatrabdois.DAO.Constants;
import com.example.agendatrabdois.DAO.DatabaseHelper;
import com.example.agendatrabdois.MODEL.Adapter;
import com.example.agendatrabdois.MODEL.Model;
import com.example.agendatrabdois.R;
import com.google.android.material.floatingactionbutton.FloatingActionButton;
import com.google.android.material.snackbar.Snackbar;

import androidx.appcompat.app.ActionBar;
import androidx.appcompat.app.AppCompatActivity;
import androidx.appcompat.widget.Toolbar;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;

import android.view.View;

import android.view.Menu;
import android.view.MenuItem;
import android.widget.AdapterView;
import android.widget.ListView;

public class MainActivity extends AppCompatActivity {
    RecyclerView lista;
    FloatingActionButton fab;

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


        lista=findViewById(R.id.lista_recycler);
        databaseHelper= new DatabaseHelper(this);



        showRecord();









        fab = findViewById(R.id.fab);
        fab.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
               startActivity(new Intent(MainActivity.this,formularioContato.class));
            }
        });
    }

    private void showRecord()
    {
        Adapter adapter;
       adapter= new Adapter(MainActivity.this, databaseHelper.getAllData());

          lista.setAdapter(adapter);
///


    }





    @Override
    protected void onResume() {
        super.onResume();
        showRecord();
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }
}