如何检查用户是否使用iOS中的FBSDKLoginKit登录？

Question

当我在viewDidLoad运行应用程序时，我需要检查用户是否之前登录过。

if FBSDKAccessToken.currentAccessToken() != nil {
    print("1")
    presentViewController(controller, animated: true, completion: nil)
} else {
    print("2")
    let button = FBSDKLoginButton()
    button.delegate = self
    button.readPermissions = ["public_profile", "user_friends"]
    view.addSubview(button)
}

它总是打印"2" 。 为什么？

Answer 1

必须在AppDelegate实现以下两种方法：

func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool {
    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)
}