what is the use of SQLiteDatabase.CursorFactory in Android?

I have created a database by extending SQLiteOpenHelper class. And its created also. This is code I am pasting

public Imagehelper(Context context) {
    super(context, DATABASE_NAME, null, SCHEMA_VERSION);

    cntxt = context;
    filename = Environment.getExternalStorageDirectory();

    DATABASE_FILE_PATH_EXTERNAL = filename.getAbsolutePath()+File.separator+DATABASE_NAME;
    Log.i("Log", ":"+DATABASE_FILE_PATH_EXTERNAL);
}

Here everything is working fine. But if you focus on the parameters pass in super super(context, DATABASE_NAME, null, SCHEMA_VERSION); . I am not able to understand the null parameter. I know here we have to pass the SQLiteDatabase.CursorFactory object.

But how?? And what is the use of that??