public void entrar (View view){
        String user = et1.getText().toString();
        String password = et2.getText().toString();

        if(password.length()== 0 || user.length()== 0) {
            Toast error = Toast.makeText(this, R.string.alert1, Toast.LENGTH_LONG);
            error.show();
        }else {
            AdminSQLiteOpenHelper conex = new AdminSQLiteOpenHelper(this,"buscaminasbd", null, 1);
            SQLiteDatabase bd = conex.getWritableDatabase();
            Cursor fila = bd.rawQuery( //cogemos la fila donde coincide el codigo
                    "select puntos from usuarios where nombre="+user, null);
            if(fila.moveToFirst()){
                String puntosj = fila.getString(0);
                Intent i = new Intent(this, Main2Activity.class);
                i.putExtra("nombre", user);
                i.putExtra("puntos", puntosj);
                startActivity(i);
            }else {
                Toast.makeText(this, R.string.alert4, Toast.LENGTH_SHORT).show();
            }
            bd.close();
        }
    }

public class AdminSQLiteOpenHelper extends SQLiteOpenHelper {

    public AdminSQLiteOpenHelper(Context context, String name, SQLiteDatabase.CursorFactory factory, int version){
        super(context, name, factory, version);
    }

    @Override
    public void onCreate(SQLiteDatabase db){
        db.execSQL("create table usuarios(nombre text primary key, pass text, puntos integer)");
    }
    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion){

    }
}