ios: programmatically ask for Game Center sign-in? - ios

I have a simple question, but I’ve looked through Apple’s documentation and done some searching and I can’t find the answer to it.
Is it possible to programmatically pull up Game Center’s sign-in view? I have a UIButton that requires Game Center, and if the client does not sign in when the app is opened (iOS pulls up the sign-in view at launch), I want to provide a second chance for the user to sign in.

I'm assuming you're calling this GKLocalPlayer method on launch: -setAuthenticateHandler: (>= iOS7) or -authenticateWithCompletionHandler: (<= iOS6)
If the user cancels the presented login screen, calling these methods again does nothing, or rather, the completion handler is called with an error. The user will then need to login to GameCenter through the GameCenter app or through the Settings app. (While testing, you can login through the GameCenter app, then logout. After that the screen can be presented in your own app again.) You can show an UIAlertView telling the user to login through the GameCenter app.
Alternatively, and I don't know if this is allowed/approvable, but in iOS7 the authenticateHandler has a viewController parameter holding the login screen. If you store this login view controller in an instance variable and the user cancels login, you can present the login screen again later using a UINavigationController.
If you try to present the saved login view controller with -presentViewController:animated:completion: the view controller's Cancel button no longer works, but using a UINavigationController hides the Cancel button and allows navigation back to your own view controller.
You'll also need to hide the login screen manually after the user logs in by responding to GKPlayerAuthenticationDidChangeNotificationName. It doesn't seem like developers were intended to be able to do this, so it may not pass approval, but it works!

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How to know coming back from Facebook?

How is it possible to test / get notification about Facebook iOS app is just left?
Implemented Facebook Login button, and when coming back from FB login screen, need to do some extra steps in my app. But viewDidAppear is not get called in that view controller.
Do you have any idea? Need to use AppDelegate methods?
You can add an observer for UIApplicationWillEnterForeground notification.
And you could add some logic right before calling the facebook button, to check if the app has entered background because of that or simply because the user has pressed home button.

App workflow of iOS app

I am making an app with 2 navigation controllers in storyboard. 1st one is LoginRootController and 2nd is RootController.
LoginRootController is set as the initial view controller. I have google and facebook login integrated to the app. Their delegates are in AppDelegate. When I login, I set RootController as rootViewController which has the home page. I'm setting this from loginButton() of FBSDK and "signIn(signIn: didSignInForUser user: withError error:)" google delegate function. There is signInSilently() and fb sign in in applicationDidBecomeActive.
The problem is that whenever signIn is called, my home page is loaded. I want to load home page only once when I login manually. What is the optimal way to do this?
I understand that you want to avoid reloading the RootController after a silent sign in triggered by the application becoming active.
The easy option is to check the current rootViewController. If it's already the RootController, no need to change it. Otherwise, change it.
Note that you probably want to save the user ID that was used to load the RootController. If that changes, you probably need to force reloading it even if it's already there.
If that's not what you want, you'll need to be more explicit and provide the relevant parts of your code.

back to previous controller before application enters background

i am developing an ios application that needs the user to login in order to get in to the system, if the user logged in and go to one of the view controllers in the application, then press home button. Now if he choose to open the application again (the application will enter forground), the application must redirect the user to the view controller he was viewing before he press the home button. Moreover, any data the user enters must be there.
Any Idea about how can I implement this in Xcode ?
Any help will be appreciated. Thanks :)
Save the viewController before app goes to background in the function applicationWillResignActive. And when app comes to foreground go to that viewController. If you have navigation based app, then call in applicationWillEnterForeground
[navigationController popToViewController:yourViewController];

How to return to app if user cancel Facebook Login?

I m working on facebook login. Everything is fine, when I tap on the login button it will take me to safari (or FB app) and ask me for FB login.
my question is how to make safari return to my app if I decide not to login and hit cancel button? its currently taking me to my facebook main page after hitting cancel and is not useful
thanks in advance!
I don't know how to do it exactly as you suggest but what you could do is create another view controller with a web view inside of it, and a navigation bar at the top that has a cancel button on it. This way they could log on to facebook from within the app, so they don't have to switch between things which can be a little lengthy! It would also allow an easy cancel button with 'dismissModalViewController' or whatever it has changed to in iOS6. I believe this should work :)

Programmatically logout in iOS application

My iOS application contains login page. And after entering the app there is a logout button. When a user presses the logout button programmatically I want to show login page again as if the user is logging first time. Could you please suggest how I could implement this in my iPad application.
I do this in my app. I have a tabbarcontroller that i use for logged in users. When they log out (or for first time use) I message the appDelegate that removes the tab bar from the window and makes the login view the root view. Once logged in, that view is replaced by the tab bar controller.
I even go a bit further. On each switch I totally release all the other objects, and so I know for sure that when user sees any of these views it's completely 'fresh' and only uses the defaults for anything custom to that user.

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