Display current username in menu

Hi,

I would like to show the logged in user’s name in the top menu. When I use this function get_current_user_id() it displays the ID number with no problem, no matter what page I am on. However when I use something like this bp_get_displayed_user_fullname() it only shows the name when I am on the profile page. When I navigate elsewhere it doesnt show anything. Is there another function I can use?

Thanks