Android rdate exception

On Android, I’ve been trying to retrieve rdate for recurring calendar event.

I’ve used the following:

Cursor cursorCalendarEvents = getContentResolver().query(
                Uri.parse("content://com.android.calendar/events"),
                new String[]{"rdate"},
                null, null, null);
        assert cursorCalendarEvents != null;
        cursorCalendarEvents.moveToFirst();
        for (int i = 0; i < cursorCalendarEvents.getCount(); i++) {
            calendarEventRTDateArr.add(cursorCalendarEvents.getString(0));
            cursorCalendarEvents.moveToNext();
        }
        cursorCalendarEvents.close();

URLs:
https://developer.android.com/reference/android/provider/CalendarContract.EventsColumns#RDATE

I get ‘null’ When I set up a recurring event.

thanks