I am making an app with different nav controllers. All of them are initially initialized.
Say, I have 3 nav controllers A, B and C.
A View controller from B (say B1) sends a notification that is supposed to be heard from view controller in A (say A1). After that, we go to view controller A1.
However, if we are in the view controller B1 from the beginning (and never went to View controller A1), then A1 doesnt get the notification. However, it gets it the second time.
OR, if I go inside A1 once, then the notifications are properly received.
Can anyone kindly help me out ? Thanks.
NB: the listeners code is in the init of A1. It gets hit (i checked by using breakpoints).
Since you're saying the notification is received after the view is displayed once, my suspicion is that you are registering for notifications in a method that isn't run until the view is displayed (viewDidLoad, viewDidAppear:, etc.).
If this is the case, try moving your notification registration to whichever init method that you're using in the ViewControllers.
NSNotification is observable through all the app. So, to do what you plan to do, I would use a boolean flag or a counter. You can put those indicators in the appDelegate class or use a global variables.
Related
I am working on an IPhone app that, through viewDidLoad, makes a connection and pulls data into a table. I would like the controller, or at least the table, to reload every time the controller is displayed, even if someone just switched from one tab to another or closed and re-opened the app on this controller. Is there a way to do this? I can't seem to find anything, it's also kind of a hard thing to search for. I have found discussions of when to put code in viewDidLoad but not another method that is run every them the controller displays.
Thanks,
Cheryl
You want to use
-(void)viewDidAppear:(BOOL)animated {
[super viewDidAppear:animated];
//code to reload table viewdata
}
Each time the view appears this method is called. I use this a lot in my app.
There's no way to do it by injecting code in only one place.
You can think of a workaround, like for example sending custom "reload request" notification from required parts of code:
viewDidAppear: in your view controller
applicationDidBecomeActive: (if table is presented)
tabBarController:didSelectViewController: (if switched onto controller with the table)
tabBar:didSelectItem: (same as above)
etc.
In you view controller simply observe this notification and reload data when required.
Although, whats more important: do you really need to reload data under such harsh requirements? In most cases data reload happens when
view controller's viewDidLoad: is called
it is manually initiated (button, for example)
long time passed since the last update was received
Otherwise it's just an overkill.
Okay, so I'm building an universal iOS app with an initial login view (view controller named LoginVC), just a plain simple UIViewController. If the login is successful the app segues to an navigation controller (MainNavigationVC). I created this segue through the storyboard gui of XCode, so no programmatic creation of the nav controller is done. The nav controller is presented modally in fullscreen, so the rest of the app is run atop the login view, with this nav controller as the centerpiece of everything.
The navigation controller contains a view (with a view controller named UserStartPageVC), and in its navigation bar is a logout button. This button sends an target action to UserStartPageVC, with the goal of dismissing the nav controller thus bringing the user back to the login view.
So far everything works fine. I can login and use the app as intended. But! When I log out and then re-login XCode tells me this:
Warning! Attempt to present <MainNavigationVC: 0x753110> on
<LoginVC: 0x756fcf0> while a presentation is in progress!
I suppose this means that the login view is trying to modally display a MainNavigationVC navigation controller, but another one is already displayed, right? But how? Can a view be presented without showing?
And how can I get rid of the old nav controller when logging out? I've tried several ways of dismissing the modal view, for instance:
from within UserStartpageVC running
[x dismissViewControllerAnimated:YES completion:NULL]
[x dismissModalViewControllerAnimated:YES]
where x is either self, self.parentViewController or self.presentingViewController.
setting the LoginVC as a property in UserStartpageVC and running
[self.loginVC dismissViewControllerAnimated:YES completion:NULL]
and so on.
All of the tested calls actually brings me back to the login screen, so it's kind of working.
Any ideas? Relevant code samples can be provided if necessary, I just couldn't figure out which pieces that were of interest. The seguing to the navigation controller has no code (except for a performSegueWithIdentifier:sender:), and the code for dismissing it is the part I cannot seem to get straight.
As a sidenote. So far this isn't a REAL problem; the app runs, and it IS possible to logout and re-login without any other side-effects than an error message in XCode. But I suppose this will be a memory leak if users logout and login multiple times, and I'm not in the mood of an unnecessary rejection from Apple.
I discovered another way to get the exact same error message. Lucky me!
If you created a segue at one point and had it tied to a button (click button -> new view) and then later give that segue a name and invoke it directly using
[self performSegueWithIdentifier:#"identifierName" sender:self];
then you can get this error because you can effectively trigger the segue twice. I thought making the button invoke an IBAction would turn off the segue I had set up in the first place, but apparently not. Hitting the button triggered the segue twice, but after I deleted the segue and re-created it as a manual segue on the view with the same identifier then I was able to invoke it via the above code and not get the warning message.
Hoopla! My bad.
Seemed I had set up the notification observing from the login API call in a stupid way. For every time the user triggered a login (or re-login), it added itself as an observer for the notification; the result was that it performed one more segue for every time a login was done.
And doing multiple segues at the same time, is... well, obviously bad.
Essentially I have a view controller where the user picks from three choices. Once the user chooses something, the view segues away to another view controller that displays some information regarding their choice for about 5 seconds and then segues back to original view controller automatically where the User must make more choices... (its basically a loop until something is accomplished).
The problem I am having is when the User touches their option, it seems to just segue back to itself without ever displaying the intermediary screen. I added a sleep(5); to the viewDidLoad but all that causes it to do is pause on the original choice screen for 5 seconds before segueing to itself. I also put in an NSLog in just to make sure it was actually using the new controller, which it is indeed.
I didn't include code since its so trivial. viewDidLoad on the new controller, has sleep(5) and the call to segue back to the original view controller.
I solved the problem by moving the code to viewDidAppear. Should have done that from the beginning honestly, just didn't think it through enough I guess.
This is my first app using storyboards/segues, and I'm pretty sure the answer to this is easy, but I'll be as thorough as possible in describing my issue.
I am making a simple app which has a Tab Bar Controller scene and two View Controllers.
My app launches by being sent a URL from another app. The application:openURL:sourceApplication:annotation: method in the app delegate performs some work to determine
which tab to display first, and
what information to display on it.
My goal is to use the performSegueWithIdentifier method (I'm open to alternatives though) from within the AppDelegate to select the tab, and also find a way to send a method to the instance of the view controller created by the storyboard.
Issue #1 is that I can't set an identifier. When I select the tab "relationship" there are no choices available in the Attributes Inspector (it says "Not Applicable"). How do I set a name for this segue? Can I? Or is there some rule under which UITabBarController segues can't be trigger programmatically?
Issue #2 is that I can't find a way to have a pointer to the view controller. Pre-Storyboard I would alloc and init a new view controller and then set it up, but here if I do that, it does not get displayed when my app launches (I think this is because Storyboard is displaying a different instance of the same view controller.)
I know this post is long, but I feel like I'm missing something simple. What is it?
Sounds like you need to have your AppDelegate set the entry point to your storybard.
I have a simple iPad application with 5 views. On the first view, the user is asked to make some selections and set some options. From this information, the other 4 views are programatically changed after an NSNotification message is sent to them. (i.e controls are added, updated).
My problem is that when the application is first loaded, the user sees View1, but View2, View3, View4 and View5 have never been opened yet, so any changes I make programatically to those views are not done and when the user navigates to them (via the tab bar) for the first time, no changes are shown.
[EDIT: I should point out that the code for making the changes to each view is contained within the ViewController itself, and is executed when the view observes the incoming NSNotification. When the view is not loaded, it understandably never received the incoming NSNotification.]
Only after the user looks at any of those screens at least once and then goes back to View1 and makes changes, are the other Views updated properly.
I thought I could get around this issue by actively loading Views 2,3,4 and 5 into memory on application start, so that they are ready to begin receiving notifications right away.
Is there an easy way to do this in iOS 5?
Why do the view changes straight away?
I would store an indicator of the changes needed when the users answers the questions on the first view and then apply the changes on -viewDidLoad of each view that needs to be changed.
Instead of trying to load the views into memory, I'd suggest you initialize these views with the options that the user set on the first view. What I usually do in such situations, when I have a global parameters that are used in many places, I create a utility class to keep the data, make it a singleton, then access the shared instance in the viewDidLoad in the views that use the data during initialization.