I am running Xcode 4.3.3 and am targeting iOS 5.1. I am attempting to include Game Center functionality in a game.
When authenticating the GKLocalPlayer the user is presented with the Sign in to Game Center alert view or shown to be logged in. So far this is all fine, but if the user presses the Create New Account button then any open modal views are moved behind the root view controller and the following error is spit from the console:
Unbalanced calls to begin/end appearance transitions for
<GKModalRootViewController: memory address>.
I have tried moving the GKLocalPlayer authentication code between the app delegate and the root view controller. I have also tried implementing the authentication in a new, blank project. I have tried it with and without Storyboards and ARC. In all of these cases the results were the same: modals hidden behind the root view controller and error given.
Here is the GKLocalPlayer authentication method I am calling from my app delegate’s application:didFinishLaunchingWithOptions: method:
- (void)authenticateLocalPlayer
{
GKLocalPlayer *localPlayer = [GKLocalPlayer localPlayer];
[localPlayer authenticateWithCompletionHandler:^(NSError *error) {
if (localPlayer.isAuthenticated) {
// Perform additional tasks for the authenticated player.
} else {
// Disable Game Center features.
}
if (error) {
// Handle error.
}
}];
}
Here is a screenshot of it. In this picture the root view controller has a background with a 50% alpha value. The modal has been pushed behind the root view controller by this bug.
This stackoverflow question contains the only reference to this error (regarding GKModalRootViewController) I can find, and it doesn't fit since (a.) I’m not using cocos2d. (b.) It happens whether or not I perform a segue, and I am not touching viewWillAppear: or viewDidAppear:. (c.) No acceptable answer was given.
This question and this one seem to involve the same issue (with the view hierarchy being destroyed) but are unanswered and don’t mention the console error message.
Does this happen for anyone else? Any ideas on what could be causing this?
UPDATE 1: I went so far as to put the authentication code into an IBAction connected to a button in the modal view so as to avoid any initialization conflicts. It didn't help.
UPDATE 2: I tried moving the authentication code into a GCD background queue. he results were the same.
Here is the test project (which is GameCenter ready with my app's Bundle ID already entered).
To test:
Log out of Game Center on the test device/simulator (if you are
logged in).
Build and run the app.
Press the info button.
Press Authenticate.
When the Sign in to Game Center alert appears press Create New
Account.
Press Cancel.
Did the “Unbalanced calls...” message appear in the console? Did the
modal view (with the Authenticate button) disappear?
Press the info button.
Did the modal display again?
This bug appears on the list of "bugs Apple fixed in 6.0". I understand you would love a workaround, but when its the APIs you depend on that are buggy, chances of that are slim.
You can however rejoice that 5.x users are slowly dying out.
Best of luck with your app.
Related
I am trying to write an App for Apple tv4 (tvos). When my App starts, the view controller does receive touchesBegan events, as it should.
Without going into too many details, the App creates, moves, and deletes sub-views to respond to the user's interactions.
After a while, the view controller does not receive touchesBegan any more (this is the strange error that I am trying to debug).
Since I think the problem has something to do with the responder chain, I have made the following two experiments:
If I let the view controller override and return true from canBecomeFirstResponder, then the problem still occurs, but it occurs much less frequently.
If I do not override that function and instead check who is the first respnder, then I find that the App has no first responder, even before the strange error occurs. That is to say, the App has no first responder even when it is working properly!
Questions: What can prevent touchesBegan from being invoked? Is it related to the responder change? If so, please explain 2 above.
How exactly are you supposed to "touch" a view rendered on a non-touch screen enabled TV?
You're not.. tvOS doesn't work like iOS in the way that you cannot detect touches because there is no touch screen enabled input device supported on an Apple TV.
Instead, you use the UIFocusEngine to handle interactions with content presented within your view hierarchy.
Check out "Controlling the User Interface with the Apple TV Remote" from Apple's Developer Library for more information.
My app uses multiple features for Apple's demo project AVCam. Everything works just fine except when I exit the app and go back in it, it doesn't show the camera preview anymore. Does anyone know what piece of code I am supposed to use and where it belongs? I tried searching but a lot of questions relating to android popped up.
You need to reinitialize your camera once the App becomes active again. In your app delegate methods, override, applicationDidBecomeActive and send a notification so your view controller knows that your app became active again.
Pending the notification received, you can reload the viewDidLoad, or move the contents of viewDidLoad to viewDidAppear. There's multiple ways to do this. You can also reload the contents of viewDidLoad in viewWillAppear. There's many many many ways to do this, like I said.
I have been all over stackoverflow and all over Google and I cannot seem to figure this one out. Here's my scenario:
I have my app's "main screen" where the user first makes decisions about what they're going to do. The app works off of a CoreData database which is created by "importing" XML files. The user can choose to open an XML file attached to an email in my application, which automatically triggers my main screen to show up and run the import of the file.
I can get this far without any issues. In my storyboard, I have a segue called ParseSegue from my main screen to a view controller which will handle the parsing and give the user some status information.
When the main screen is called via the email app, the main screen automatically calls
[self performSegueWithIdentifier:#"ParseSegue" sender:self];
I then check for this segue name in prepareForSegue and it's a valid name. This is where I assign the file URL to the parser controller so that it can parse the correct file.
The problem is that the segue never actually happens. The prepareForSegue method gets called, the name "ParseSegue" can be checked against and is valid, but the segue itself simply does not happen. If I add a button to the main screen and tell it to perform the segue within the storyboard, it works fine. But calling it programmatically seems to do nothing.
It turns out that I was looking in the wrong place entirely. My problem was that in my appDelegate, where the app reacts to the incoming URL, I was inadvertently creating a new instance of my storyboard and my main view controller. This was different than the one which was already active and may or may not have been on the screen.
The controller I was creating was never actually shown. I only noticed this because the log:
NSLog(#"Source: %#", [segue.sourceViewController description]);
would show different memory addresses for my test (the button push) and the import test. This led me to believe that I was, in fact, working with two different instances of the storyboard and the app's main view controller. Thanks to Paul for the suggestion of logging the destination and the source controllers.
In my project I show an Alert to the user to indicate an 'empty list'.
Right now, I show it in AppDelegate>applicationDidBecomeActive.
I'm doing this because I want the alert to show if the list is empty
at app startup and when coming out of the background (iOS 4.2 through 5.x).
EDIT:
I use a method in the AppDelegate, and call it with a slight delay, and I still get this notice.
[self performSelector:#selector(checkForNoMessages) withObject:nil afterDelay:1.0];
However, this causes a "wait_fences" notice in the debugger and I'd prefer not to submit to Apple with this notice.
Where is the proper place to put a popup Alert so that it appears:
1) At App startup
AND
2) When the App is coming out of the background?
Do I need the Alert in more than one place?
I recommend writing a method in your AppDelegate or better in your root view controller which shows the message. Maybe with some arguments, so you can reuse it but that's up to you.
If you are following the MVC architecture ask your model about existing entries and trigger the Alert message if necessary. But encapsulate this behavior in a controller as well.
application:didFinishLaunchingWithOptions: and applicationDidBecomeActive: are the places where you want to delegate this task to your controller.
More about iOS Multitasking: https://developer.apple.com/library/ios/#documentation/iphone/conceptual/iphoneosprogrammingguide/ManagingYourApplicationsFlow/ManagingYourApplicationsFlow.html
Edit:
Don't forget that you have to call the methods from the main thread.
And do all startup stuff first.
OK - the problem wasn't where I called the alert, it was because it was in a method. Once I moved the code from a method into applicationDidBecomeActive, all is well.
In my app there is authentication required, so when you launch one of the tabs on tab bar, "class A" checks are there credentials saved if not, "class B" modal view controller with fields to login launches.
So my question is : in which method in class A (loadView, viewWillAppear or maybe in another one) should be implemented checking if there are credentials saved and other stuff described above.
And my additional second question is:
is pushing modalviewcontroller correct way to show login screen, or i should do that differently?
Thank you for reply guys.
OH ! One More Thinh
And one more thing. I've done implementing LoginView by adding delegate and presenting ModalVC (Harkonian the Piquant's method). But in my tab bar app i have got very confusing problem. I mean when user taps login button (assume that everything was correct and he's able to secured data) how PROPERLY switch to tab where is secured info. I mean previously selected tab.
i did it by adding in
-(IBAction) login {
//some code
self.tabBarController.selectedIndex =1;
And it seem to work good but is it correct ?
I have a very similar use case in my app -- it requires a passcode to authenticate. After a lot of testing and tweaking I found the following design to be the best approach:
Don't use class A to launch your credentials VC -- use the app delegate instead.
For security purposes, typically you'll want the credentials VC to show before the user can view the underlying view. It's much easier to handle this in the app delegate than in a VC. In addition, you need to consider what happens when your app is backgrounded -- a screen shot is taken of the current state of the app. If you are using viewController A to show the credentials view, when the app relaunches the user will be able to see whatever sensitive information was visible on app close until the app finishes launching and VC A presents the credentials VC.
Don't insert your credentials view into an existing ViewController -- use a new UIWindow instead.
You don't ever want any other view to be able to sit on top of your credentials view. Ever. Even views that would normally always be on top, like UIAlertView. The easiest way to achieve this is to have a special UIWindow just for your credentials view. Show this window and hide the primary app window whenever you need to display the credentials view.
How does this approach look in practice?
If you are at all interested in how well this design works, you can check out the passcode feature in Audiotorium Notes for iPad. I spent a lot of time with this design to make sure it was as secure as possible.
If you have any specific implementation quests feel free to ask and I'll try to answer them.