how to create a database and fill it in sqlite android?

I'm having a problem with creating a sqlite database for my android app. I'm using SQLiteOpenHelper class, I have successfully created the database and i am sure of that through logCat but I think I'm failing to create a table and fill it with dummy data just to simulate a login procedure.I Just want to create the database and create a table inside of it and insert some data in the table, i want to do that in the onCreate method of another activity. I will show you what i have tried.

Here is the SQLiteOpenHelper class:-

public class DBHandler extends SQLiteOpenHelper {
private static final int DATABASE_VERSION = 1;
private static final String DATABASE_NAME = "qpc.db";
public static final String TABLE_USERS = "users";
public static final String COLUMN_ID = "_id";
public static final String COLUMN_USERNAME = "username";
public static final String COLUMN_PASSWORD = "password";
public DBHandler dbHandler;


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



@Override
public void onCreate(SQLiteDatabase db) {
    String query = "CREATE TABLE " + TABLE_USERS + "("
            + COLUMN_ID + " INTEGER PRIMARY KEY AUTOINCREMENT,"
            + COLUMN_USERNAME + "Text ,"
            + COLUMN_PASSWORD + "Text );";
    db.execSQL(query);

    ContentValues contentValues = new ContentValues();
    contentValues.put(COLUMN_USERNAME,"test");
    contentValues.put(COLUMN_PASSWORD,"123");
    db.insert(TABLE_USERS,null,contentValues);

}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    db.execSQL("DROP TABLE IF EXISTS " + TABLE_USERS);
    onCreate(db);
}


public void open() throws SQLException
{
    dbHandler.getWritableDatabase();
}


public void close()
{
    dbHandler.close();
}

public boolean login(String username, String password){
    SQLiteDatabase db = getReadableDatabase();
    String query = "SELECT "+ COLUMN_ID + " FROM " + TABLE_USERS +
            " WHERE username= "+ COLUMN_USERNAME +
            " AND password= "+ COLUMN_PASSWORD + ";";


    Cursor cursor = db.rawQuery(query,new String[]{username,password});
    int count = cursor.getCount();
    if(cursor != null) {
        if (count > 0) {
            return true;
        }
    }
    return false;
}

Here is how I call it in the LoginActivity

public class LoginActivity extends ActionBarActivity {
    private static Button loginBtn;
    public static EditText usernameTxt,passwordTxt;
    private static String writtenUsername,writtenPassword;
    private Users user;
    private DBHandler dbHandler;

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

    //identifying login button
    loginBtn = (Button) findViewById(R.id.loginButton);

    //identifying username editText
    usernameTxt = (EditText) findViewById(R.id.username);

    //identifying password editText
    passwordTxt = (EditText) findViewById(R.id.password);

    dbHandler = new DBHandler(this, null, null, 1);


    //check if database exists
   File dbtest = getApplicationContext().getDatabasePath("qpc.db");
    if(dbtest.exists())
    {
    Log.d("Database23", "exists");
    }
    else {
        Log.d("Database23", "doesn't exist");
    }
}

//handling login button
public void attemptLogin(View view){
    //getting what was written in username and password editText
    writtenUsername = usernameTxt.getText().toString();
    writtenPassword = passwordTxt.getText().toString();
    try {
        if (!writtenUsername.matches("") && !writtenPassword.matches("")) {
            if (dbHandler.login(writtenUsername, writtenPassword) == true) {
                Toast.makeText(this, "yes", Toast.LENGTH_SHORT).show();
            } else {
                Toast.makeText(this, "no", Toast.LENGTH_SHORT).show();
            }
        } else {
            Toast.makeText(this, "Please fill all fields", Toast.LENGTH_SHORT).show();
        }
    }catch(Exception e){
        Toast.makeText(this,e.getMessage(), Toast.LENGTH_LONG).show();
    }
}