I am in the process of building a reasonably complex iPad app that will run on iOS7+. The app has a login screen that must be accessed once every user session, this is the starting view controller in my storyboard. The user can log out from any other screen in the app (there are about 60 other screens) by touching a button that is always available in every other ViewController. When the user logs out, a custom transition animation should be used.
It seems I can achieve this in one of two ways, either with a segue from every screen in the app to the login page, which makes the storyboard impossible to read, or presentViewController.
I've implemented this with presentViewController, by looking up the view controller by id from the storyboard (which creates a new instance, which is a desired behavior) and then presenting it from the current view controller.
Not surprisingly, this does not dismiss the original login view controller and essentially creates a stack of view controllers, eventually I run out of memory as each time a user logs out, a new login view controller is created and retained.
Is there a way to clear this "stack" of view controllers?
Is there a different way to present a view controller, with an animation, that does not involve presentViewController or segues? I've considered view controller containment, but that doesn't seem quite right when used with storyboards.
Have you considered replacing the root view controller? If the app delegate observes a logout notification and replaces the root view controller with the initial content of the storyboard that should get the app back to the initial screen.
I've seen that presented as a solution for login/logout issues elsewhere on the web, but I'm not sure if there's a transition you can animate there.
I think your approach is wrong. Correct me else wise.
Login mechanisms are supposed to be singleton instances. Hence you should define your view controllers, models, views all as singleton instances. Please look at my following code for example.
static id objectInstance;
+ (id) sharedInstanceID {
if (!objectInstance) {
objectInstance = [[YourClass alloc] init];
}
return objectInstance;
}
Let me know if this helps you.
Related
On the home vc, there is a button that allows the user to select a picture. I'm wondering the better approach for when the button method is called.
Option A: Present ImagePickerController modally on the root view controller, acquire picture, and push a new view controller that deals with the picture.
Option B: Push a new vc, add ImagePicker modally onto 2nd view controller, acquire picture, and deal with the picture on that same view controller.
I would suggest following B if you have any substantive work to do with the picture before returning to the root. For two reasons:
It reduces specific code in the root Controller
If you need to do this someplace else eventually, it will be easier to reuse
Also, I would suggest having the root register itself as a delegate of the new VC and have the new VC call a delegate method when finished. It is normally the best pattern for controller reuse in a case like this.
I'm working on a app which uses the controller containment pattern as described in the View Controller documentation in the iOS SDK.
I've written the controller container, and it works great. My controller is basically containing two sub views and it displays them both at the same time, sliding one over the other depending on what the user is doing. Works wonderful.
Now, I want to use this container controller in a navigation view. This is to get push segues to work. In effect, from my contained controllers, I want to be able to use the navigation stack, push a new controller on, and pop when the user is done.
However, I have noticed that if the navigation view is instantiated with my container controller as the root container, things fall apart.
In particular, I have noticed this:
In the iOS documentation, container controllers call addChildController: and then addSubview:. This seems to break the navigation stack, as the push segue does not work - it behaves like modal. I believe it does this because addSubview resets the navigation stack.
I confirmed this by replacing addChildController and addSubview with [self.navigationController pushViewController...]. I confirmed it is a problem with addSubview because I can reproduce the issue when I omit the call to addChildController.
When I do this, the navigation stack works properly. But of course, my container controller does not, as only the "most recently pushed" controller is visible.
I'm doing this because in my contained controllers, I want to push a new controller onto the stack, and when the user is done, I want to "pop" the stack, without reloading the "previous controller".
Using a modal segue reloads the previous controller; using a push controller does not.
I cannot find any documentation on the behavior of addSubview and it's effect on the navigation stack.
Thank you in advance for any light you guys can shed!
I'm having a bit of trouble completely understanding what you are doing, but I think that what you want to do is exactly what I'm doing.
I have a UINavigationController that has as its rootView a container UIViewController. That controller adds children per the normal methods. One of those children views pushes other views that may get popped.
One of those pushed views COULD message the appDelegate and make itself the rootViewController if it wanted to. In general, as long as you keep a strong reference to a view controller, you can remove it from whoever 'owns' it, and muck around with the navigationControllers viewControllers array to your hearts content.
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.
Hi there and thank you in advice for your help. I have a really strange problem while working with ViewControllers in Xcode4. First of all I have to say that I'm not using storyboards and I prefer to create any UI element programmatically. So I've set a UIButton and I want that, when pressed, it brings me to a new view controller. This is the code I'm using for a button:
-(void)settingsAndExportHandle:(UIButton *)buttonSender {
SettingsViewController* settingView = [[SettingsViewController alloc] initWithNibName:#"SettingsViewController" bundle:nil];
settingView.modalTransitionStyle = UIModalTransitionStyleFlipHorizontal;
[self presentModalViewController:settingView animated:YES];
}
This buttons is initialized and allocated in the viewDidLoad method of the RootViewController. I want to switch to the other view controller (in this case SettingsViewController) when I press the button.
The strange thing is that when I press the button, the animation that flips the controllers goes well, but when it finishes I obtain the EXACT same things that I had on the RootViewControllers (same custom views, same buttons, same all!). The question is: what I'm missing?? I have to say that I use ARC (automatic reference counting) so I can't release or dealloc the views and buttons I've created on my RootViewController.
Any help will be appreciated. Thank you all!
Pushing and and modally presenting view controllers does not deallocate the view controller that presented them. It simply adds the additional view controller to the stack. You'll need to implement a callback method so that when the user hits the button to flip back to root view controller, your settings view controller lets the root view controller know what's about to happen so you can call a method you've written to reset the interface back to whatever state you need it at. You may also be able to use viewWillAppear: but that's a little messy.
However, according to the Apple Human Interface Guidelines, the user expects that when they push a view controller or modally present it, the view controller they were on will save state and be exactly the way they left it when they came back. It's disconcerting and annoying when state is not preserved while in a navigation controller context. It is especially annoying when it's modally presented.
Think about this - A user is in a hypothetical Mail app. They start typing out an email and set a font size and a color. They tap on the add attachment button, which brings up a modal view controller that allows them to select a picture. They select the picture and the modal view is dismissed, and in your implementation, the mail composing interface would have reset and the email content would be gone or at the very least the selected font size and color would be back to the default. That's not a good experience.
I'm having trouble to achieve the following using a storyboard:
When setup is not done:
run app -> show settings view controller -> show main navigation controller
When setup is done:
run app -> show main navigation controller
So basically, I want the app to programmatically start with the settings view in certain cases, and otherwise skip right ahead to the main navigation controller.
I did manage to show the settings view with a modal style segue from the main navigation controller, but I don't know how to display it before the main navigation controller is displayed. Any ideas?
By default, the initial view controller from your main storyboard is instantiated and displayed automatically when your app starts up. To prevent this happening you need to remove the UIMainStoryboardFile setting from your info.plist file.
With no default view controller, you are now free to create one programmatically at app startup. See the UIStoryboard documentation. Use +storyboardWithName:bundle: to load the storyboard and then use –instantiateViewControllerWithIdentifier: to create the correct view controller. You will also need to create a main UIWindow and add the view controller's view to it just like you used to do with .nib based UI. Note that without the UIMainStoryboardFile setting a main window is not created for you - read the explanation.
I managed to do it a bit different:
Use a UINavigationController as the initial view controller.
Create a root view controller that will manage the decision of what to load.
Create a Storyboard Segues from the root view controller to the main view and to settings view, and give the segues proper identifiers.
Call the performSegueWithIdentifier with the proper identifier from your root view controller.
Just another solution, hope this helps.
I did something similar to amoshaviv, his advice is sound. I did it slightly different though, and I'll give some more info.
I created a custom MyInitialViewController class, derived from UIViewController, and made this the initial view controller.
In the storyboard file, I created modal segues with appropriate names to all (in my case three) possible 'real' first view controllers.
In the MyInitialViewController class, I implemented the
- (void)viewDidAppear:(BOOL)animated;
method, to first perform the check which view to switch to, and then do the correct
[self performSegueWithIdentifier:#"NameOfSegue" sender:self];
Effectively, this makes the MyInitialViewController nothing more than a switch performed when it's brought into view. I first tried doing this when loaded because I don't care for actually seeing this view, but that did not work, while viewDidAppear does.
To make this visually smooth, I tried the following. In the properties of the segues, I disabled animation. The view I left empty, and I gave it a background color matching to that of the startup image.