Do not create my database in SQLite

I have a problem with an exercise that I am doing, I am working with android studio and the DBNavigation plugin, I am trying to create a database with a table and a record, but I do not believe any of the three things but it does not shoot me either error, and check the configuration of my database and everything seems correct, the database is created in a dialog box to register a new user.

This is my database:

In this class I create a new database:

package com.example.enriq.almacenamiento_en_android_enrique_espinosa;

import android.app.Activity;
import android.content.Context;
import android.content.DialogInterface;
import android.database.sqlite.SQLiteDatabase;
import android.support.v7.app.AlertDialog;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.support.v7.widget.GridLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.widget.EditText;
import android.widget.Toast;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;

import static android.os.Environment.getExternalStorageDirectory;

public class MainActivity extends AppCompatActivity {
    AlertDialog alertDialog1;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }

    public void OnClicRegistro(View view){

        CreateAlertDialogWithRadioButtonGroup();

    }

    public void CreateAlertDialogWithRadioButtonGroup() {

        AlertDialog.Builder builder = new AlertDialog.Builder(MainActivity.this);
        LayoutInflater inflater = this.getLayoutInflater();
        View MyView = inflater.inflate(R.layout.dialog_signin, null);

        final EditText nusuario = (EditText)MyView.findViewById(R.id.nusuario);
        final EditText ncontrasena = (EditText)MyView.findViewById(R.id.ncontrasena);
        final EditText ncontrasenar = (EditText)MyView.findViewById(R.id.ncontrasenar);

        builder.setView(MyView)
                .setPositiveButton("Registrar", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int id) {
                        if(nusuario.getText().toString().equals("") || ncontrasena.getText().toString().equals("") || ncontrasenar.getText().toString().equals("")){
                            Toast.makeText(getApplicationContext(),"Tienes que llenar todos los campos", Toast.LENGTH_SHORT).show();
                        }else{

                            SQLiteDatabase myDatabase = openOrCreateDatabase("Examen", MODE_PRIVATE ,null);
                            myDatabase.execSQL("CREATE TABLE IF NOT EXISTS usuarios("+
                                    "id INTEGER PRIMARY KEY AUTOINCREMENT,"+
                                    "nombre_usuario TEXT NOT NULL,"+
                                    "password TEXT NOT NULL,"+
                                    "passwordr TEXT NOT NULL);");

                            myDatabase.execSQL("INSERT INTO usuarios(nombre_usuario, password, passwordr) VALUES(\"Enrique\",\"kikelau123\",\"kikelau123\");");
                            Toast.makeText(getApplication(),"El usuario se registro correctamente", Toast.LENGTH_SHORT).show();
                        }
                    }
                })
                .setNegativeButton("Cancelar", new DialogInterface.OnClickListener() {
                    public void onClick(DialogInterface dialog, int id) {
                        Toast.makeText(getApplicationContext(),"No se ha registrado un nuevo usuario", Toast.LENGTH_SHORT).show();
                        alertDialog1.dismiss();
                    }
                });
        alertDialog1 = builder.create();
        alertDialog1.show();

    }

}