Facebook SDK ios login button исчезает после одного входа

Question

Я пытаюсь реализовать вход в facebook. Я начал работать с несколькими учебниками, но после того, как я вошел в систему и снова открыл приложение. Кнопка входа в систему исчезла. Я пробовал очистить проект, снова открыть, и когда я воссоздал все, то случилось то же самое испытание. Вот мой код:

App делегат:

// 
// AppDelegate.swift 
// Click 
// 
// Created by Emlyn Mileaf-Patel on 11/29/15. 
// Copyright © 2015 Emlyn Mileaf-Patel. All rights reserved. 
// 
// borrowed code from: http://www.brianjcoleman.com/tutorial-how-to-use-login-in-facebook-sdk-4-0-for-swift/ 

import UIKit 
import FBSDKCoreKit 
import FBSDKLoginKit 

@UIApplicationMain 
class AppDelegate: UIResponder, UIApplicationDelegate { 

    var window: UIWindow? 

    func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool { 
     // Override point for customization after application launch. 
     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 applicationWillResignActive(application: UIApplication) { 
     // Sent when the application is about to move from active to inactive state. This can occur for certain types of temporary interruptions (such as an incoming phone call or SMS message) or when the user quits the application and it begins the transition to the background state. 
     // Use this method to pause ongoing tasks, disable timers, and throttle down OpenGL ES frame rates. Games should use this method to pause the game. 
    } 

    func applicationDidEnterBackground(application: UIApplication) { 
     // Use this method to release shared resources, save user data, invalidate timers, and store enough application state information to restore your application to its current state in case it is terminated later. 
     // If your application supports background execution, this method is called instead of applicationWillTerminate: when the user quits. 
    } 

    func applicationWillEnterForeground(application: UIApplication) { 
     // Called as part of the transition from the background to the inactive state; here you can undo many of the changes made on entering the background. 
    } 

    func applicationDidBecomeActive(application: UIApplication) { 
     // Restart any tasks that were paused (or not yet started) while the application was inactive. If the application was previously in the background, optionally refresh the user interface. 
    } 

    func applicationWillTerminate(application: UIApplication) { 
     // Called when the application is about to terminate. Save data if appropriate. See also applicationDidEnterBackground:. 
    } 


} 

View Controller:

// 
// ViewController.swift 
// FacebookTutorial 
// 
// Created by Brian Coleman on 2015-03-27. 
// Copyright (c) 2015 Brian Coleman. All rights reserved. 
// 

import UIKit 
import FBSDKCoreKit 
import FBSDKLoginKit 

class ViewController: UIViewController, FBSDKLoginButtonDelegate { 

    override func viewDidLoad() { 
     super.viewDidLoad() 
     // Do any additional setup after loading the view, typically from a nib. 

     if (FBSDKAccessToken.currentAccessToken() != nil) 
     { 
      // User is already logged in, do work such as go to next view controller. 
     } 
     else 
     { 
      let loginView : FBSDKLoginButton = FBSDKLoginButton() 
      self.view.addSubview(loginView) 
      loginView.center = self.view.center 
      loginView.readPermissions = ["public_profile", "email", "user_friends"] 
      loginView.delegate = self 
     } 

    } 

    override func didReceiveMemoryWarning() { 
     super.didReceiveMemoryWarning() 
     // Dispose of any resources that can be recreated. 
    } 

    // Facebook Delegate Methods 

    func loginButton(loginButton: FBSDKLoginButton!, didCompleteWithResult result: FBSDKLoginManagerLoginResult!, error: NSError!) { 
     print("User Logged In") 

     if ((error) != nil) 
     { 
      // Process error 
     } 
     else if result.isCancelled { 
      // Handle cancellations 
     } 
     else { 
      // If you ask for multiple permissions at once, you 
      // should check if specific permissions missing 
      if result.grantedPermissions.contains("email") 
      { 
       // Do work 
      } 
     } 
    } 

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

    func returnUserData() 
    { 
     let graphRequest : FBSDKGraphRequest = FBSDKGraphRequest(graphPath: "me", parameters: nil) 
     graphRequest.startWithCompletionHandler({ (connection, result, error) -> Void in 

      if ((error) != nil) 
      { 
       // Process error 
       print("Error: \(error)") 
      } 
      else 
      { 
       print("fetched user: \(result)") 
       let userName : NSString = result.valueForKey("name") as! NSString 
       print("User Name is: \(userName)") 
       let userEmail : NSString = result.valueForKey("email") as! NSString 
       print("User Email is: \(userEmail)") 
      } 
     }) 
    } 
} 

Answer 1

Я думаю, ваша проблема здесь:

if (FBSDKAccessToken.currentAccessToken() != nil) 
     { 
      // User is already logged in, do work such as go to next view controller. 
     } 
     else 
     { 
      let loginView : FBSDKLoginButton = FBSDKLoginButton() 
      self.view.addSubview(loginView) 
      loginView.center = self.view.center 
      loginView.readPermissions = ["public_profile", "email", "user_friends"] 
      loginView.delegate = self 
     } 

отладки и проверки, которые оператор ввода когда ваше представление загружено, кажется, что FBSDKAccessToken.currentAccessToken() не ноль.