Cannot set the checkbox using a given custom class

I'm following these classes in order to get a spinner with an item and a checkbox:

android spinner dropdown checkbox

The problem is, I can't actually maintain the state of the checkbox. I'm able to set them giving them a value from a Database, but When I close the spinner to click on update (and send the values to the BD), the values reset. I've been spending many hours in a working solution, but I found nothing.