Upvote:3
You must understand the nature of "sponsorship" in a Schengen visa. Unless your friend signed a VerpflichtungserklΓ€rung, he is just providing extra information about your travel plans. The visa officials will look for the answers to several questions:
So if you are planning to stay in Barcelona for one or more nights, you should explain where in Barcelona you are staying. A hotel booking is one option, and probably the best if you plan to stay in a hotel.