I am a newbie to iOS world and have started building custom code on top of a templated code.
So excuse me for the obvious.
The View chain starts with a MainWindow.xib which contains a App Delegate Object, a Window Object and Application ViewController. I dont understand why those objects are needed over there. But what I understand, I need to mention starting ViewController in the "Nib Name" Property to initiate my custom View Controller (called "EmptyViewController"). Its a dummy view controller, just there to avoid crash to happen as a result of missing valid viewcontroller.
I initiate a separate Modal View Controller(MainViewController) inside didFinishLaunchingWithOptions.
Code for initiating modal View Controller --
self.window.rootViewController = self.viewController;
mainView = [[MainViewController alloc] initWithNibName:#"MainViewController" bundle:nil];
// present the viewcontroller
UINavigationController *navController = [[UINavigationController alloc] initWithRootViewController:mainView];
[self.viewController presentModalViewController:navController animated:NO];
// release it, because it's retained as modalViewController
[navController release];
I do not put this MainViewController inside MainWindow.xib as I want to have navigation at the root of MainViewController.
Inside MainViewController, I push HelpViewController when "help" button is pressed.
But HelpViewController does not show any navigation bar. I do not understand why?
Code for Pushing Navigation bar --
HelpViewController *helpVC = [[HelpViewController alloc] init];
[self.navigationController pushViewController:helpVC animated:YES];
[helpVC release];
So I would like to understand --
1) Why is MainWindow.xib needed? Can I remove it? (Note: I tried to remove it, but then I get blank screen)
1.a) Why are all the controls/objects App Delegate Object, a Window Object and Application ViewController objects needed?
2) Why doesnt HelpViewController show Navigation bar?
3) Another thing I noticed, if I say self.presentingViewController, EmptyViewController handle is returned while popViewController returns me back to MainViewController.
Thanks
The App Delegate simply implements some app-level 'callbacks' by which iOS communicates with your own code. In main.m you can see how iOS is told which of your classes implements UIApplicationDelegate. iOS creates an instance of this class and call these delegate methods ('callback') whenever appropriate (e.g. when the app goes to background).
The Window is something iOS provides, your app needs to tell what to display on it. And, as you saw, this is usually done in didFinishLaunchingWithOptions (which is called by iOS to inform your app things are ready to get started).
A View Controller is a class that handles states of stuff you show on the Window. You don't show stuff directly on the Window, but instead use Views. Every View Controller has a View with UI elements.
The XIB or NIB is a UI description/layout file. A XIB and View are linked together; you need to tell the XIB to which View Controller member (e.g. a UILabel) a UI element belongs, and you tell the XIB which View Controller method to call on a certain UI event (e.g. user taps on a button).
These are the basics. I'm aware it does not answer all your questions; I suggest you read the very good Apple documentation. Don't try to understand everything immediately as things, as you're experiencing, indeed can seem illogical at start.
So let's say I have a viewController named homeViewController, and another view controller named listViewController
I display listViewController on top of homeViewController as a modal.
If the user clicks the off button, and then comes back to the app the modalViewController is gone.
ListViewController *listViewController = [[ListViewController alloc] init];
[self presentModalViewController:listViewController animated:NO];
[listViewController release];
Note: Application doesn't startup from scratch when this occures and the previous state is still visible
I'm assuming that by "off button" you mean the user locks the iDevice.
I just tried this in one of my apps and the modal view controller is still there after unlocking. My guess would be that it's something unrelated to the code you have posted. I would check your - (void)applicationWillResignActive:(UIApplication *)application method in your app delegate class and see if there's anything there that would dismiss the modal view controller.
Here is what the problem was.
When the user locks the screen I remove homeViewController from window
[homeViewController removeFromSuperview];
When user starts the app again I do
[windows addSubview:homeViewController];
that brings homeViewController on top of its modeal
I keep getting the following errors:
2011-04-02 14:55:23.350 AppName[42430:207] nested push animation can result in corrupted navigation bar
2011-04-02 14:55:23.352 AppName[42430:207] nested push animation can result in corrupted navigation bar
2011-04-02 14:55:23.729 AppName[42430:207] Finishing up a navigation transition in an unexpected state. Navigation Bar subview tree might get corrupted.
2011-04-02 14:55:23.729 AppName[42430:207] Finishing up a navigation transition in an unexpected state. Navigation Bar subview tree might get corrupted.
Here is what I am doing. From a view controller, I call the following when a certain button is pushed:
EventsViewController *viewController = [[EventsViewController alloc] init];
UINavigationController *navController = [[UINavigationController alloc] initWithRootViewController:viewController];
navController.navigationBar.tintColor = [UIColor blackColor];
[self presentModalViewController:navController animated:YES];
[viewController release];
[navController release];
Then, if a certain button is pushed in EventsController, I call:
SingleEventViewController *viewController = [[SingleEventViewController alloc] initWithEvent:[currentEvents objectAtIndex:indexPath.row]];
[self.navigationController pushViewController:viewController animated:YES];
[viewController release];
Then, if a certain button is pushed in SingleEventViewController, I call:
EventMapView* viewController = [[EventMapView alloc] initWithCoordinates];
[[self navigationController] pushViewController:viewController animated:YES];
[viewController release];
So yea, it's obvious that there's nested push animations, but isn't this the right way to go about it? I checked out Apple's DrillDownSave code and this appears to be how they're doing it. Does it matter that I use init methods instead of viewDidLoad methods?
Calling pushViewController before viewDidAppear is unsafe.
ACCIDENTLY TRIGGERING THE SAME SEGUE TWICE
Once in code, and once from interface builder, but both at the same time...
I was getting the same error as the rest of you. Only my problem was I was accidentally firing the same segue, twice. Once from interface builder, and once from within my code.
I have a UITableView. When a cell is selected, a segue in interface builder fires. Heres my problem, I had the segue set up to be directly fired off clicking the CELL ITSELf, inside interface builder, then in my code, I had under didSelectRowAtIndexPath, code that would fire that same segue... like so...
[self performSegueWithIdentifier:#"MySegue" sender:tableView];
That means when didSelectRowAtIndexPath gets called because a row was selected, it fires the segue with the above line of code. Then interface builder, also triggers the segue, because its connected directly to the cell object in interface builder. To stop interface builder from directly firing the segue. You have to connect the segue from the top of the view controller, not nested down inside coming off of the cell itself.
So if you are having this problem for the same reason as me, that is, you are calling the same segue twice, you can fix this by unlinking the connection from the CELL DIRECTLY, to your segue, and having the segue connection originate at the top of the table hierarchy in IB, rather than nested inside the cell. Connect the segue from you View Controller itself, to the segue. If you have done this correct, when you select the segue, it should highlight the ENTIRE view it is coming from, not just the cell.
Now Apples documentation states thus under the performSegueWithIdentifier:sender: reference:
Apps normally do not need to trigger segues directly. Instead, you configure an object in Interface Builder associated with the view controller, such as a control embedded in its view hierarchy, to trigger the segue. However, you can call this method to trigger a segue programmatically, perhaps in response to some action that cannot be specified in the storyboard resource file. For example, you might call it from a custom action handler used to process shake or accelerometer events.
In my case, I have a search button for my UITableView, and whether the segue is called when the search results table is present, or the normal table view is present, had to be determined. So I needed to trigger the segue directly.
So remove the embedded control from interface builder, and just stick it on the view controller itself, then trigger the segue in your code!
Now, no more double segues! And no more errors.
I had the same problem / error message as you did just now, was looking for a solution and ended up at this thread, however, for me I found that the solution is actually having only one animated:YES when doing a nested push (I put animated:YES only for the final push), hope this helps
cheers.
I've figured it out. Apparently if you call -pushViewController from outside of the -didSelectRowAtIndexPath method of a UITableViewDelegate, it doesn't work. Moving the call into that function worked. Weird.
I happened upon this same problem that resulted from a button in a nib being connected to two different actions. It tried loading both view controllers, thereby corrupting the stack.
What do you mean when you say you use init methods instead of viewDidLoad methods?
If you're pushing a new view controller before the old push has bad a chance to be actioned, you will get this sort of error. So putting certain code into init and doing things prematurely could certainly get you the error being reported.
At the point where init is being run on a view controller, the view hasn't been loaded yet!
Um I had this issue, and Im new to the whole iOS dev scene. But after looking at my connections inspector (with file's owner) in the interface builder i saw that as I had copied a button it had the previous buttons method assigned to it as well as the new method I had created. I guess that was where the nested aspect of my problem came from, as it was executing 2 different methods both of which pushed a view onto the Nav Controller. I know this has already been answered but I figured I would put this up just in case anyone else had a silly mistake like mine.
This has already been answered, but I thought this might help others as I got the same error but without using table views. I finally figured out the problem.
I had an existing button whose IBAction invoked a pushViewController. I had created a new button by copying the existing button. The new button also had an action that invoked pushViewController. When the new button was tapped (touch up inside) and the view controller was pushed, I got this error. I deleted the new button, created it from scratch, bound it to the existing outlets and actions, and the error went away.
Ran into the same problem. In my case I was missing a break in the switch statement so two segues were fired at the same time. Easy fix for me.
My problem had to do with the keyboard being active.
This was caused for me by pushing a ViewController from a textField's delegate method:
-(void)textFieldDidBeginEditing:(UITextField *)textField{
FilterLocationViewController *destViewController = (FilterLocationViewController *)[self.storyboard instantiateViewControllerWithIdentifier:#"FilterLocationViewController"];
[self.navigationController pushViewController:destViewController animated:YES];
}
By changing the code to this:
-(void)textFieldDidBeginEditing:(UITextField *)textField{
[_textFieldLocation resignFirstResponder]; //adding this line
FilterLocationViewController *destViewController = (FilterLocationViewController *)[self.storyboard instantiateViewControllerWithIdentifier:#"FilterLocationViewController"];
[self.navigationController pushViewController:destViewController animated:YES];
}
(adding the line [textField resignFirstResponder];) the problem went away.
Basically the lesson is that you shouldn't modify the navigationController stack if the keyboard is out.
Recently, I've faced the same problem. The reason was: -I was trying to pop view controller twice by mistake. you can check this crash by setting breakpoints on push and pop View controllers
1) Perhaps you could try passing the necessary variables as properties before pushing the UIViewController rather than using the init methods with parameters. Most likely you will need these parameters beyond your init method anyway.
Also, in your initWithCoordinates: method you are missing the parameters. Possibly your custom init methods are a part of the problem.
2) Just because you mentioned viewDidLoad -- this method is for initialization after a view has loaded . If you create the UIViewController in code, as it seems you do, you should use loadView to set up your subviews.
This was happening for me because of my UIControlEvents
[button addTarget:self action:#selector(callSecondView) forControlEvents:UIControlEventAllTouchEvents];
I had to change the UIControlEventAllTouchEvents to UIControlEventTouchUpInside or however you want your button to work if you had the issue because of a UIButton call.
My Solution was
[self performSelector:#selector(moveTo) withObject:nil
afterDelay:0.5];
Don't know about other's. I think most of the People using StoryBoard is facing such Problem. I am using XIB.
In my case The Problem Was, when I was moving to another view using push,
I was also using
[self.navigationController popViewControllerAnimated:YES];
in the ViewWillDisappear of the current View at the same time. Just remove it and it works fine.
I was using POP, because of the requirement and the Flow.
The Hierarchy was 1 -> 2 ->3
I was on view 2 and wanted to move to view 3. In that case I encountered this error.
In my case I was both setting the push segue from the storyboard and programatically. Hopefully that'll help anyone
I had this error message too, and the navigation bar and navigation controller transitions were weird. My setup was a bunch of Navigation Controllers embedded in a Tab bar Controller. The problem was that I didn't call super.viewDidLoad() in my Tab bar Controller implementation of viewDidLoad.
Calling super is something the docs clearly point out that you should do when overriding viewDidLoad, and I learned this the hard way.
Maybe this can help someone else too!
I know that this was answered, but it could help others.
I had the same problem, but it was caused because I was using a bad event for an info button.
I was using "UIControlEventAllTouchEvents" and this generated two push of the same view into the navigation controller. The correct event was "UIControlEventTouchUpInside". I'm new to iOS.
This resolves the problem:
https://github.com/nexuspod/SafeTransition
If you push (or pop) a view controller with animation(animated:YES) it doesn't complete right away, and bad things happen if you do another push or pop before the animation completes.
To reproduce this bug, try pushing or popping two view controllers at the same time. Example:
- (void)viewWillAppear:(BOOL)animated
{
[super viewWillAppear:animated];
UIViewController *vc = [[UIViewController alloc] init];
[self.navigationController pushViewController:vc animated:YES];
}
You will receive this error:
2014-07-03 11:54:25.051 Demo[2840:60b] nested push animation can
result in corrupted navigation bar 2014-07-03 11:54:25.406
Demo[2840:60b] Finishing up a navigation transition in an unexpected
state. Navigation Bar subview tree might get corrupted.
Just add the code files into your project and makes your navigation controller as a subclass of APBaseNavigationController, and you'll be good to do.
Just to complete the list, here is another reason which can cause "nested push animation can result in corrupted navigation bar":
I did setup several NavigationController within a TabBarController and set
the selectedIndex within the storyboard Identifiy Properties. After moving active Tab to Code error disappeared.
i created a navigation based project but instead of tableview i added a new view with a button to navigate to the other view.. my button code is as shown below but whenever i run it the application doesn't run?? is the code wrong or navigation based application only work with tableview??
-(IBAction)clickMe:(id)sender
chdDetails *details=[[chdDetails dalloc]initWithNibName:#"chdDetails" bundle:nil];
[self.navigationController pushViewController:details animated:YES];
[details release];
details=nil;
It says "[[chdDetails dalloc]initW.... instead of alloc. is that a copy-waste typo?
No a navigationCOntroller will work with any viewController, you don't even need the navigationbar. I bet most application are navigationBased but you don't even see it.
[self.navigationController.navigationBar setHidden:YES]
Will do that.
Try placing a breakpoint in the clickMe method to test if it even gets called. What does this mean: "the application doesn't run??" is there an error message? Have you hooked the button up in IB? Is chdDetails a subclass of UIViewController? etc. etc.
Is chdDetails an UIViewController or an UIView? You can't push an UIView on an UINavigationController, only controllers.
I recently started a project, using Apple's Utility Application example project. In the example project, there's an info button that shows an instance of FlipSideView. If you know the Weather.app, you know what the button acts like.
I then changed the MainWindow.xib to contain a scrollview in the middle of the window and a page-control view at the bottom of the window (again, like the Weather.app). The scrollview gets filled with instances of MainView. When I then clicked the info button, the FlipSideView would show, but only in the area that was previously filled by the MainView instance – this means that the page-control view on the bottom of the page still showed when the FlipSideView instance got loaded.
So, I thought that I would simply add a UIViewController for the top-most window, which is the one declared inside the AppDelegate created along side with the project. So, I created a subclass of UIViewController, put an instance of it inside MainWindow.xib and connected it's view outlet to the UIWindow declared as window inside the app delegate. I also changed the button's action, so that it know sends a message to the MainWindowController instance. The message does get sent (I checked with NSLog() statements), but the FlipSideView doesn't get shown. Here's the relevant (?) code:
FlipsideViewController *controller = [[FlipsideViewController alloc] initWithNibName:#"FlipsideView" bundle:nil];
controller.delegate = self;
controller.modalTransitionStyle = UIModalTransitionStyleFlipHorizontal;
[self presentModalViewController:controller animated:YES];
[controller release];
Why's this not working from inside of MainWindowController, but the exact same code is working from inside of MainViewController? I've uploaded the entire project here for you to be able to see the whole thing.
Thanks for help!
-- Ry
EDIT: I think it might be related to me attaching the UIViewController's view outlet to an UIWindow instance. I now connect it to a UIView, and it's working perfectly well.
For the record, the answer has been added in the question. Ryyst said:
I think it might be related to me
attaching the UIViewController's view
outlet to an UIWindow instance. I now
connect it to a UIView, and it's
working perfectly well.