If you have an event (e.g. onchange), the context object can be passed to the page (show a page). If the category is an attribute of your passed object, you can use this in your page.
Basically, as below:
Domain model:
Example of listview: a list of objects of the entity Category:
E.g. action button. See the Events section. Category will be passed to the page:
Example page which expects the Category object as page parameter. This is a dataview with entity Category: