SSO in iphone, OAuthException

if I use safari to authorize user with facebook everythig work, but if use native application i have error:

{
   "error": {
      "type": "OAuthException",
      "message": "Error validating access token: Session has expired at unix time 1315843200. The current unix tim开发者_StackOverflow社区e is 1315919174."
   }
}

if I tried log out and next log in, I got same access token. How may I resolve this problem?

If you get OAuthException you need simply to reauthorize.

Also when your app is started you need to make a call to graph API "me" and in case you get exception you need simply to re-authorize, then you proceed with regular workflow of API calls.

You can make your access_token not to expire by requesting offline_access extended permission, but it still might be invalidated.

hope this helps