Checking username and password in Android using SQLite database

I want to get query from SQLite Database in my APP that consist of name, surname, username and also password.

when I click login button, it made crash. here is my code ##

public String Login(String Username, String Password) {


    String Q = "SELECT * FROM " + DBHelper.TBLname + " WHERE "
            + DBHelper.ColumnUser + " = " + Username
            + " AND " + DBHelper.ColumnPass + " = " + Password;

    Cursor LoginQuery = MyDB.rawQuery(Q, null);

    if (LoginQuery == null) {
        LoginQuery.close();
        String LoginResult = "Wrong User Name and Password";

        return LoginResult;
    }
        LoginQuery.moveToFirst();
        String LoginResult = LoginQuery.getString(3);
        LoginQuery.close();
    return LoginResult;
}

Answer

Try this without dbhelper:

SELECT * FROM YOUR TABLE WHERE Username=Your Username AND Password=Your Password