The reason of passing null is you want the standard SQLiteCursor behaviour. If you want to implement a specialized Cursor you can get it by by extending the Cursor class( this is for doing additional operations on the query results). And in these cases, you can use the CursorFactory class to return an instance of your Cursor implementation. Here is the document for that
SQLiteDatabase.CursorFactory DOC
Used to allow returning sub-classes of Cursor when calling query.