What is the function responsible for opening the nav drawer?

In my application I work with the menu Navigation Drawer . I had a question - what function is responsible for opening the curtain. It means - there is a hamburger, which you can click on to open a list with menu items, or simply open it with a swipe. I wonder what function is responsible for creating menu items there. The question is caused by the fact that I need to independently fill in the title + subtitle + imageview that are in the menu header. This header consists of view elements that I want to fill with data from the server, and I need to send a request for information not when creating the whole menu, but only when the curtain opens, because when creating the menu, the request is sent, and two requests run very crooked. Therefore, it is interesting how to send a request only when the curtain is activated.