FBSDKAccessToken.currentAccessToken（）发现没有

Question

我只是将facebookm集成到我的应用程序中。但每次FBSDKAccessToken.currentAccessToken（）都发现没有，所以我无法获取用户数据。这是我的代码

override func viewDidLoad() { 

    if (FBSDKAccessToken.currentAccessToken() != nil)
    {
        print("Not loggedin...")
    }
    else
    {
        print("logged in...")

    }

    loginbutton.delegate = self
    loginbutton.readPermissions = ["public_profile", "email", "user_friends"]
    FBSDKProfile.enableUpdatesOnAccessTokenChange(true)



}
func loginButton(loginButton: FBSDKLoginButton!, didCompleteWithResult result: FBSDKLoginManagerLoginResult!, error: NSError!)
{

    if((FBSDKAccessToken.currentAccessToken()) != nil){
        FBSDKGraphRequest(graphPath: "me", parameters: ["fields": "id, email, first_name, last_name"]).startWithCompletionHandler({ (connection, result, error) -> Void in
            if (error == nil){


                let email = result.valueForKey("email") as? String
                let fbid = result.valueForKey("id") as! String
                let fname = result.valueForKey("first_name") as! String
                let lname = result.valueForKey("last_name") as! String
                print(email)

            }
        })
    }
}

func loginButtonDidLogOut(loginButton: FBSDKLoginButton!) {
    print("User Logged Out")
}

或在appdelegate

  return FBSDKApplicationDelegate.sharedInstance().application(application, didFinishLaunchingWithOptions: launchOptions)




}



func application(application: UIApplication, openURL url: NSURL, sourceApplication: String?, annotation: AnyObject) -> Bool
{
    return FBSDKApplicationDelegate.sharedInstance().application(application, openURL: url, sourceApplication: sourceApplication, annotation: annotation)
}


func applicationDidBecomeActive(application: UIApplication) {

    FBSDKAppEvents.activateApp()

}

所以这是我的代码，但每次我得到的结果都没有价值，当我的结果显示它没有可用的变量。所以哪里出错了