anyway to tell if a user has app installed using facebook?

Is there anyway to know if a user has a app installed dy using Facebook? I was thinking there may be a way because it asks for permissions from the user, so I'm sure its something that registers. I want to be able to tell a user if any friends on Facebooka parti开发者_如何学运维cular app installed that uses Facebook. If so tell them who.

Try this FQL.

SELECT uid, name, pic_square FROM user WHERE is_app_user  AND uid IN (SELECT uid2 FROM friend WHERE uid1 = me())

I can see an Android Tag. Try this Android Application (component)

Saved me a week of questioning how to make Facebook, android application

If you want to be able to post something to their wall through your application after authorization, YES. With the proper privileges, I suppose you could then query their friends feeds to see who else has a similar post on their wall. This may not be a very reliable method though if it works because people can just delete, and often do delete their posts from apps. See these links to help you with this.

Authentication - http://developers.facebook.com/docs/authentication/

Mobile Apps - http://developers.facebook.com/docs/guides/mobile/

edit: nice answer regarding the FQL queries, use that.