Android app widget preferences

Question

I am building an android app that has a list of objects, and every object has a field category which can be one of three possible categories.

There is an app widget that is 3x3 in size and has a list of mentioned objects in it. Now, I need to filter the list every time app widget is created. User goes to the widget page from the home screen, selects my list widget and when he/she drags it to the home screen, there should pop WidgetSettingsActivity that offers the user to filter the list with one of the three categories.

I am starting the activity from widget class with

        Intent i = new Intent(context, WidgetSettingsActivity.class);
        i.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
        context.startActivity(i);

But when and where should I call it to get the dialog for every widget when the user sets it on the home screen?