Android badge/ item counter on each product category

Question

I try to develop a simple Shopping list app with different ptoduct categories like "dairy", "meat" etc. For each category there is a different ListView. When the user choose category - the new list opens and he can add items.

Now I would like to show to the user:

1. simple TextView with some 'V'simbol for each category with items
2. or (prefer) something like badge with count items for every category.

I know how to add badge icons for categories in XML, but I'm still not fully understand what exactly (and where) I have to add in Java MainActivity ...

Thanks for any help!