The Problem
I'm currently building an iPad game using SpriteKit. The gameplay is driven by sound provided by EZAudio. After running the Instrumentation tools to profile my app, I noticed that whenever the GameViewController is shown memory allocation jumps up. When I repeatedly show the screen (5+ times) it crashes the app. My project uses ARC.
Navigation
The navigation consists of 4 ViewControllers:
MenuViewController: This shows the menu
CharacterSelectionViewController: It lets you a pick a character to use
GameViewController: This lets you play a game with the player chosen
ScoreViewController: It shows you the score you achieved in the game
1 - MenuViewController
From here you can navigate to CharacterSelectionViewController via a Show (e.g. Push) segue.
2 - CharacterSelectionViewController
You can navigate to GameViewController via a Show (e.g. Push) segue. There is also a back button that goes back to MenuViewController with the following code:
[self.navigationController popViewControllerAnimated:YES];
3 - GameViewController
It first shows a 5 second countdown (using NSTimer)
The game starts with the character chosen in CharacterSelectionViewController
The game can be paused, allowing you to quit and go back to MenuViewController via a manual Show Detail (e.g. Replace) segue.
When the game ends, a manual Show (e.g. Push) segue is called that navigates to the ScoreViewController.
It's view hierarchy consists of three sets of view - one for the countdown, one for the pause menu and one for the game. These are subsequently shown/hidden. See the view hierarchy below:
4 - ScoreViewController
This allows you to quit or restart the game. When quit it pressed it performs a Show Detail (e.g. Replace) segue to MenuViewController. If restart is pressed it performs an unwind to CharacterSelectionViewController.
Responses
Please provide answers regarding:
How this kind of leak could occur
Any observations you have from the allocation and leaks screenshots
Allocation
Below, you can see the increasing allocations as I cycle through the apps screens to repeatedly show the GameViewController. I used Mark Generation to be able to show the increase in memory allocations.
Leaks
Here you can see the memory leak that occurred. This is ordered by size.
Ignore the leaks for the moment; fix the generational accretion first.
Is that generation snapshot representative of what is left after a typical snapshot? Typically, you'd want to show view controller, take snapshot, hide then show view controller, take snapshot, etc... as many times as you can without crashing (or 10 times if it doesn't crash).
Then look at generation 3 or 4 as that'll be the most stable representation of per-generation accretion.
If it is representative, it looks like you are leaking everything that the view controller would normally allocate. Ultimately, you are looking for the "root" of your object graph that is keeping everything around. Fix the reason why the root is sticking around and the rest'll likely go away.
I wrote a weblog post about this. It is a bit outdated, but the analysis workflow remains the same.
http://www.friday.com/bbum/2010/10/17/when-is-a-leak-not-a-leak-using-heapshot-analysis-to-find-undesirable-memory-growth/
How are you unwinding from your various view controllers? I note that you mention that when the game ends you're pushing another VC onto the stack, but I presume this VC chain will at some point unwind back to your initial menu? (In essence, I wonder if you're just looping around, hence adding new VCs to the stack everytime you play a game.)
To create an un-wind segue, simply create an empty method in the destination VC (i.e.: your main menu) as such:
- (IBAction)unwindToMainMenu:(UIStoryboardSegue*)sender
{
// Intentional NOP
}
(N.B.: Make sure it's also listed in the header.)
You can then call this as you would any other segue in your storyboard by dragging from the source object in question to the exit option at the top of the VC that contains the source object in the storyboard. This will present you with a list of segues to choose from. (You can verify that the segue is setup correctly by selecting the source object in the storyboard - the Connections inspector should list the unwind segue within the Triggered Segues section.)
Related
Basic question:
Is there a reliably way to trigger showing modal UIViewControllers at any point in the app's lifetime (including from different threads)?
My current approach is to call presentViewController on the showing ViewController (found through window.rootViewController + hierarchy traversing but that's unimportant). This generally works, but is sometimes ignored due to things like a navigation action/animation taking place.
E.g. a background thread signals for a popup to be shown, and presentViewController is called on a ViewController in the process of being dismissed.
I've tried a few work arounds such as repeating the signal if the ViewController isn't shown (which led to some instances of it being show multiple times), but it's ended up being a game of whackamole.
An ideal solution would also allow navigation to take place underneath the popup, but the primary issue right now is just reliability.
edit
To be clear, I’m a seasoned developer. The threading is being handled properly, the instance and type management is working. My problem is trying to manage all
the corner cases, not the basics of how to do it.
If you need mechanism for thread safe showing different VCs in multithread environment, you can make some object which is responsible for presenting/dismissing controllers. And make some queue on presenting/dismissing. So when your signal occurs, your operation on presenting will be next after dismissing current VC in queue
I got some serious problems understanding the viewcontroller stack.
When will my app use a stack to save the previous viewcontrollers? Only if I use a navigation viewcontroller or anytime I use normal viewcontrollers and segue modally between them?
So I was just wondering if I use some sort of chained routine for example, like going from vc 1 to vc 2 and from vc 2 back to vc 1. No navigation controller, just modal segues, no unwinding.
Does my app got performance issues because of a stack (which will grow everytime I go around) or doesn't it make any difference?
----updated
So basicly this is my problem. If I went through the routine of the app, the views get stacked everytime I do a transtition.
UINavigationController will retain any controller you push onto it's navigation stack until you pop it back off.
Any UIViewController will retain a controller it presents modally until that child controller is dismissed.
In either case every controller will at a minimum consume some memory until you remove it. Apps which construct ever expanding stacks of controllers are likely to encounter a number of issues including:
you will eventually run out of memory, how fast depends on how much memory each controller uses.
you may see unexpected side effects if many controllers in the background react to the same event.
users may become confused if they change state in an instance of controller 'A', push an instance of controller 'B' on top of it, and then "return" to a second instance of 'A' added to the top of the state. Since they're looking at a new controller and view whatever selection, scroll position, user input, or other state they set on the previous instance may be lost.
developers, including you, may come to dread touching this app.
I suspect that everyone will have a better experience if you view controller management matches whatever visual metaphor you are presenting to the user.
I am building an application in Xcode 6.2, for iOS 8.1. I have a UIViewController (LevelViewController) which contains a UICollectionView whose cells each represent a level in my game (each one has a label w/ a number). Once one of the cells is selected I perform a show segue to an SKScene which loads all the data for that particular level.I also have a "menu" button which performs a show segue back to the main menu.
Functionally this all works, however I am having serious memory problems after performing both segues. After peeking in instruments it appears that when I segue out of the LevelViewController that all of the UILabel that I added for each individual UICollectionViewCell remain in memory, along with everything else contained in the cells. There should only be 192 labels (for 192 levels) but after performing this segue several times they add up to around 1000 in instruments.
Obviously these are not being deallocated in memory, It's my understanding that swift should take care of that, so i'm not sure what the problem is. I should also note that the UICollectionView was added programmatically, and no IBOutlets are used.
So how exactly can I get rid of those labels, and really, the UICollectionView itself when I segue away from the LevelViewController. Im seriously confused about this and it's ruining my St. Patricks Day. So for the love of all things Irish please help a lad out :)
Note: methods I have tried
self.collectionView.removeFromSuperView()
self.collectionView = nil
self.collectionView.deleteItemsAtIndexPaths(path)
It's hard to tell without seeing the code you're using to perform these segues. But I'm guessing that the problem has to do with how you are segueing between the view controllers.
I also have a "menu" button which performs a show segue back to the main menu.
If I had to guess based on your language above, instead of popping the Level ViewController (I'm assuming it is embedded in a UINavigationController), you are trying to segue back to the main menu using performSegueWithIdentifier: This will actually create a new instance of the view controller and push it onto the navigation stack (and retain the existing instance of it leading to your memory woes).
If that's indeed your problem, the solution is pretty simple: When your menu button is tapped, you should be calling popViewControllerAnimated or dismissViewControllerAnimated:completion:.
A simple little thing worth doing while you get accustomed to iOS segueing is to add de-initializers to all your view controllers as follows so as to get ongoing debug messages that objects are being deallocated as expected:
deinit {
debugPrintln("Name_of_view_controlled deinitialized...")
}
Happy St. Paddy's Day!
I changed navigation in my application from using UITabBarController to u UINavigationController. I.e. former solution (1st version) was based only on the TabBarController - 4 ViewControllers (one simple TableView, one simple custom view and one MapView with many overlays). The second version is based only on the UINavigationController.
In case of TabBarController it was clear and simple, everything worked fine, especially MapView. I mean: the MapView was loaded once (with a significant number of overlays) and when I went to another view and back to the MapView the MapView was still there with its overlays already loaded and displayed (simple check: MapView`s viewDidLoad was called just once per app run, I had some debug messages there).
Now I changed navigation logic to the UINavigationController. Everything works fine for the first look - but: the viewDidLoad (for each view) is called everytime I navigate to the view. It is annoying especially in the case of the MapView - the loading of overlays is performed everytime, it takes some time and it causes app crash in some cases.
OK, my questions:
Is it some kind of "common" behavior of NavigationController?
Can I change this behavior so viewDidLoad will be called just once?
And more - How can I influence the "display sequence" of some view?
I understand the logic is probably more complicated but I appreciate any answer or hint ;)
Some related circumstances:
TabBar and Navigation controllers are not combined.
I use storyboards, segues are designed in the UIB, no manual calling like perfomSegue or prepareForSegue in my code. One button triggers segue to MapView.
I use push segues.
I also tried to use modal segues but without any change of that behavior.
any of viewDidUnload is never called during segues among the views.
No memory warning received.
No memory leaks measured both on simulator and iPhone 4.
I tried to build a very simple temporary project / app that is concerned just about the Nav. Controller and other views without ANY coding, just storyboard. It was the same behavior.
There was an issue that causes app crash when I fast and periodically tapped to navigation button and back button between one view and the MapView. In most cases the app crashed when I tapped the back button on the MapView before it was fully displayed (i.e. its overlays). It was fixed when I added a 1 sec. delay method call in the viewDidDisappeared in the MapView. It is not a fair fix, I know ;)
A UITabBarController and UINavigationController are based on fundamentally different paradigms.
The UITabBarController is intended for the UIViewController on each tab to exist independently of each other and for the user to choose which they want to view. viewDidLoad only gets called once for each UIViewController because it is intended that each tab still exists in memory even as the user switches to a different tab.
The UINavigationController is a stack of UIViewControllers where each is related to the one above and beneath itself. The top UIViewController in the stack is always the one that is visible to the user. When a UIViewController is pushed to the stack, its viewDidLoad gets called because it is being loaded into memory. When the top UIViewControllergets poped off the stack, it is unloaded from memory, and viewDidUnload gets called on the way out (viewDidUnload is deprecated in iOS6 and won't get called, but the controller will still get dumped from memory). This is why viewDidLoad gets called every time that the user pushes a particular UIViewController onto the UINavigationController stack.
I have a fairly simple app thats a game for small children. There is a main screen and 5 separate levels. 3 of the 5 levels are made up of more than one VC where actions take place in the first VC in that row then code calls a modal segue to the next one in the line and so on till it reaches the end of the row and a modal segue is called linking back to the main screen. The levels that have only one VC just perform actions then segue back to the main VC.
Every segue in the app in modal.
Also every page (VC) has a home button that will segue to the main page if pressed
I set this all up in the StoryBoard and visually everything works as Id expect but when adding sound I realized that there seems to be a major problem.
If I now understand correctly (and maybe I dont) modal segues dont actually replace the current VC with the newly requested one but rather slide the newly requested one over top the original and make it the visible display.
Currently I go from main to level 1. Level 1 does some stuff and plays some sounds that repeat via a timer. If I segue back to main visually everything is fine except the sounds being played by the timers in level 1 VC continue to play and xCdoe give me the following error quite a few times
2013-01-21 22:16:07.901 TTBetaDev[678:c07] Warning: Attempt to present <MainMenuViewController: 0x7e02f40> on <BonusViewController: 0x7ecbfa0> whose view is not in the window hierarchy!
Below is a screenshot of my storyboard in case I havent explained the layout well enough.
How should this be set up to allow the navigation I would like? A what steps will I need to take to apply that to the what I already have built in the storyboards? Or will I have to re-do all my storyborad work?
I tried apples VC documentation but I couldnt understand what relates to what Im trying to do.
COuld someone please help explain this to me
You have segues going forwards AND backwards. You shouldn't do this.
e.g. Look and Main and VC 2.
You have a segue going from Main to VC 2. This means that Main will present VC 2 as a modal view controller.
When Main does this though it is still on the stack underneath VC2.
Then you have a segue from VC2 to Main. This means that VC2 will create a new Main and present it modally too. If you continue using the app you will have multiple instances of main and all the other VCs and memory consumption will rocket.
What you need to do is delete ALL the segues that go backwards. (i.e. like the one from VC2 to Main)
Then when you want to get back to main from VC2 you have to dismiss VC2.
i.e.
in Main...
//present VC2
[self performSegueWithIdentifier:#"VC2Segue" sender:nil];
//dismiss VC2
[self dismissViewController:vc2ViewControllerInstance];
or in VC2...
//dismiss VC2 from itself
[self dismissViewController:self];
The main thing though is that you can't use segues to go backwards.
TL:DR
Nothing should segue INTO Main. Any segues that go into the left hand side of main should be deleted and dealt with properly.