Hello, I'm looking for information on sharing on facebook a screenshot.

Since the GameSparks service uses Facebook API to connect (?)

Does that mean that in order to post on facebook a screenshot I would need to ask again the player his crendentials?

Platform is Android using Unity 5

regards

Yes of-course.

In-fact we just provide the access token to GameSparks (I mean permission for logging in is handled by us).

As Facebook updated its rules, I remember it wont allow auto post. When ever we need to post an image, it will be only by user interaction. User will accept the new permission for publish- If not done earlier.(This needs a review from Facebook as well when you are publishing your game).

Just to cross check, Does your FB.IsLoggedIn returns false on new launch?

To clarify, If Facebook is already logged in, and you already accepted the permission earlier, it should not ask the credentials again. In that case, it will directly popup the share dialog.

 I have not code it yet, so far I'm 80% complete with the leaderboard part, which works OK. Until now I have only used the Access Token, but I assume it will work OK after switching to the FacebookConnectAuthenicate (?).But since I have not seen that GameSparks has the "share on facebook" feature, I was being concerned to have to ask twice user credentials to logging and then to post his progress on Facebook.

The way we handle Login part and give access token to Facebook, the same way Sharing part needs to be handled by us. 

If Facebook maintains the session(if logged-in status in FB sdk is maintained), then it will directly prompt you the share dialog. else it may prompt for user login which is acceptable as the user isn't logged in yet.

In short, What I saw was, Gamesparks doesn't offer share and is left to us to implement those specific social network features.