My friend is a poser?

Honestly, I would just confront him about this. From experience, I had friends wanting to be "cool" and not be themselves. I usually confront them about how I feel,THEN leave (to prevent further drama). This will allow him to think about him not being himself. If he becomes less selfish and talk to you, then you know you did the right thing. If not, then you know he's not a good friend.