DB with adapter

MainActivity.java

package myitschool.com.databaseapp;

import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ListView;
import android.widget.SimpleAdapter;
import android.widget.Toast;

import java.lang.reflect.Array;
import java.util.ArrayList;

public class MainActivity extends AppCompatActivity {
    DBHelper dbHelper;
    ListView lvMain;
    SQLiteDatabase db;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        lvMain = findViewById(R.id.listview);
        db = openOrCreateDatabase("players.db", MODE_PRIVATE, null);
        db.execSQL("CREATE TABLE IF NOT EXISTS scores (id INTEGER PRIMARY KEY AUTOINCREMENT, nickname VARCHAR(10), score INTEGER)");
        String nameGen[] = {"KA", "PI", "PO", "ELON", "MUSK", "RO", "MI", "LER", "ZIN", "GO"};
        addRecord(nameGen[(int)(Math.random() * nameGen.length)]
                + nameGen[(int)(Math.random() * nameGen.length)],
                (int)(Math.random() * 100) * 5);
        showDB();
    }

    public void addRecord(String nickname, int score) {
        db.execSQL(String.format("INSERT INTO scores (nickname, score) VALUES ('%s', %d)", nickname, score));
    }

    public void showDB() {
        Cursor c = db.rawQuery("SELECT * FROM scores", null);
        int nicknameIndex = c.getColumnIndex("nickname");
        int scoreIndex = c.getColumnIndex("score");
        Log.d("MAIN_ACTIVITY", Integer.toString(nicknameIndex) + " - " + Integer.toString(scoreIndex));
        ArrayList<String> data = new ArrayList<>();
        if (c.moveToFirst()) {
            do {
                Toast.makeText(getApplicationContext(), c.getString(nicknameIndex), Toast.LENGTH_SHORT).show();
                Toast.makeText(getApplicationContext(), c.getInt(scoreIndex) + "", Toast.LENGTH_SHORT).show();
                data.add(c.getString(nicknameIndex) + " " + c.getInt(scoreIndex));
            } while (c.moveToNext());
        }
        ArrayAdapter adapter = new ArrayAdapter(getApplicationContext(), android.R.layout.simple_list_item_1, data.toArray());
        lvMain.setAdapter(adapter);
        adapter.notifyDataSetChanged();
    }

}