How to get Facebook login token, after OK button clicked in “You have Already Authorized APPName” facebook

Question

I am using xamarin.forms PCL having android and IOS Project

following below is step:

• I have not login with facebook app in my iphone.

• when I try to register with facebook, safari open, Pop up message open "You have Already Authorized APPName"

• I click OK button,then again popup "open page in APPName". I click OK button

I get token = null and Iscancel = true;

Below is my code:

public class FacebookLoginButtonRenderer : ButtonRenderer
{

    protected override void OnElementChanged(ElementChangedEventArgs<Button> e)
    {
        base.OnElementChanged(e);
        if (Control != null)
        {
            UIButton button = Control;

            button.TouchUpInside += delegate
            {
                HandleFacebookLoginClicked();
            };
        }
    }

    private void HandleFacebookLoginClicked()
    {
        LoginManager manager = new LoginManager();
        manager.Init();
        manager.LogOut();
        manager.LoginBehavior = LoginBehavior.SystemAccount;

        manager.LogInWithReadPermissions(new string[] { "public_profile", "email", "user_birthday" }, (result, error) =>
          {
              if (error != null)
              {
                  App.OnFacebookAuthFailed();
                  return;
              }
              else if (result.IsCancelled)
              {
                 return;
              }
              else {
                  var UserToken = result.Token.TokenString;
                  if (UserToken != null)
                  {
                      var request = new Facebook.CoreKit.GraphRequest("/me?fields=id,email,first_name,last_name,gender,birthday", null, UserToken, null, "GET");
                      request.Start((connection, result1, error1) =>
                      {
                          if (error1 != null)
                          {
                              new UIAlertView("Error...", error.Description, null, "Ok", null).Show();
                              return;
                          }
                          var obj = result1 as NSDictionary;
                          FBModel fb = new FBModel();

                          fb.ID = obj["id"].ToString();
                          fb.Name = obj["first_name"].ToString();
                          fb.Email = obj["email"].ToString();
                          fb.LastName = obj["last_name"].ToString();
                          fb.Gender = obj["gender"].ToString();
                          if (obj.ContainsKey(new NSString("birthday")))
                          {
                              var birthdate = obj["birthday"].ToString();
                              fb.Age = DateTime.Today.Year - Convert.ToInt32(birthdate.Split('/')[2]);
                          }
                          else
                          {
                              fb.Age = 25;
                          }

                          App.OnFacebookIOSAuthSuccess(fb);
                      });

                  }
              }
          });
    }
}

When I login in Facebook app then this code work perfect.

Please suggest me where I am going wrong. How can I get the token?

Answer 1

1)Open Safari browser

2)Logout Facebook

3)Open App and Again Login Facebook

   private void HandleFacebookLoginClicked(){

   LoginManager login = new LoginManager(); 
   login.LogInWithReadPermissions(readPermissions.ToArray(),
   delegate(LoginManagerLoginResult result, NSError error)

 {
    if (error != null)
     {
      App.OnFacebookAuthFailed();
     }
    else if (result.IsCancelled)
     {
       App.OnFacebookAuthFailed();
     }
     else
     {
       var accessToken = result.Token;
       App.OnFacebookAuthSuccess(accessToken.TokenString);
      }
      });
    }


     public override bool FinishedLaunching(UIApplication app, NSDictionary options)
    {

       FBSettings.DefaultAppID = FacebookAppId;
       FBSettings.DefaultDisplayName = FacebookAppName;


        return base.FinishedLaunching(app, options);
    }


    public override bool OpenUrl(UIApplication application, NSUrl url, string sourceApplication, NSObject annotation)
    {
        base.OpenUrl(application, url, sourceApplication, annotation);
        return FBSession.ActiveSession.HandleOpenURL(url);
    }

    public override void OnActivated(UIApplication application)
    {
        base.OnActivated(application);
        // We need to properly handle activation of the application with regards to SSO
        // (e.g., returning from iOS 6.0 authorization dialog or from fast app switching).
        FBSession.ActiveSession.HandleDidBecomeActive();
    }
}