I'm writing a navigation app for iPhone at the moment and I'm having a very weird crash issue and was wondering if anyone had come across (and solved) this issue.
I have two views, both of which contain UITableViews and one that uses cells loaded from a nib. When I push and pop from one view to the other, after a couple of presses (usually 7 to 10) with everything loading and displaying as it should the app suddenly crashes. The debugger shows that CALayer was the last thing running, but I don't use any custom implementation of this class.
My first thought is that I've over-released an object, but after two days of playing with the code I can't identify any zombies.
Does anyone know what's going on here? Can post parts of code if required.
UPDATE:
Looks like zombies are being created on UIView delegate methods, namely viewWillAppear, viewDidAppear, viewWillDisappear, viewDidDisappear. Will investigate further tomorrow. :D
What you can do is to set breakpoints at the dealloc methods of the related classes, and see if the crash happens in one of the method. And also usually by looking at the callstack when the crash is happening, you can tell whether it's a memory related crash or not.
Related
I made a universal application that contains NIB files for both ipad and iphone UI's. In my view controllers initWithNibName method I call UIUserInterfaceIdiomPad == UI_USER_INTERFACE_IDIOM() to detect whether the controller is running on iphone or ipad.
I then launch their respective nib files. When I run the app on iphone, it works fine, but when I run it on ipad it eventually crashes with a EXC_BAD_ACCESS error. This error occurs when I use a view controller to launch another view controller, which then launches another one in the navigation stack. This error occurs as soon as I click the view that belongs to the third controller of the stack.
I cannot distinguish a difference between the NIB files that would cause a crash. I have been working tirelessly to figure out why this is happening but I cannot fix this error. Does anyone have any insight into what might be going on?
Any advice on how to approach fixing this problem would be very appreciated.
The first thing you should do is enable the "All Exceptions" break point. This will often accurately tell you the line of code where the EXC_BAD_ACCESS is happening.
Next, I would turn on zombies and see where the over-release is happening. To do so, in Xcode, while holding the option key, click Product | Run.... In the ensuing window, add NSZombieEnabled to the environment variables list.
Then run. Do the normal things you do to cause the crash and see where the debugger lands. With any luck, it will stop where the problem is actually occurring.
When you get a EXC_BAD_ACCESS it means you're trying to access/release something that's already been released. If you're in a non-ARC situation, it normally means you've inadvertently released something when you didn't mean to, so just check for alloc/init and release balance. If, however, you're in an ARC situation, I would bet it has to do with not niling a delegate when a view controller gets released.
For example, if you have a MKMapView and have set its delegate to your view controller, you should nil its delegate when your view gets unloaded or dealloc'd. Otherwise, messages will continue to get set to it. Or, another possibility is that you've added your view controller as an NSNotificationCenter observer and didn't remove it as an observer when the view controller was unloaded or dealloc'd.
Another possibility is that you're re-using view controllers between the two versions of your universal app. If you are accessing anything by an identifier that doesn't exist in the nib for the iPad, that would cause a crash--though if you're using nibs as opposed to storyboards, that may not be an issue.
That's about all I can think of for now. Try to zero in on where it's happening and post code here if you still can't figure it out.
Best regards.
I have a simple UIViewController whose view is created via a Nib. Here's the structure of the Nib:
And a screenshot of the layout:
Whatever the previous view (there are 2 possibilities), there is significant stutter/lag when transitioning to this view. Even the keyboard animation is lagged. Also, this is only on an actual device.
I've tried removing the MKMapView to see if that was the case, but it didn't make a difference.
Is the Nib too complex? Should I load everything via code? I'm not sure what it could be, but its really annoying, especially when the rest of the app is super crisp.
As far as code goes, its nothing special: just alloc/init a view, push it onto a UINavigationController, etc. Nothing in the viewWillAppear:/viewWillDisappear:.
Coming from Reddit, where you posted code (probably want to do that here too):
My guess would be the lag is coming from the section from line 44 through 80ish, where you build the overlay. Something in there might be taking longer than you think (Spotpoint unSerialize sounds fishy). You typically want to do as little work as possible in viewDidLoad, since that is called as the UI is transitioning to the new view controller.
Try throwing that code into a GCD queue or running it in the background, and see if that helps the loading stutter.
I have a problem I can't locate clearly, maybe you can help me...
I have an iPad project, based on UINavigationController, most (but not all) of controllers inside are instances of UITableViewController, and everything works well...
Everything excepting that my application crashes randomly, sometimes after 10 minutes of use, sometimes after only 10 seconds...
It never crashes on the same view, never at the same time, making that difficult to reproduce.
In addition, it only seams to happen on device, I've never got this crash in the simulator.
The debugger doesn't help me very much, here is what it says:
-[UITableView autorelease]: message sent to deallocated instance 0x8e9800
And here is the call stack:
http://i.stack.imgur.com/JSCHx.png
Any idea ?
Thanks (and sorry for my english)
You're overreleasing a UITableView somewhere in your code. Are you calling release or autorelease on the UITableView inside one of your UITableViewControllers? You should only release objects that you 'own'. You get to own an object by using methods beginning with alloc, new, copy, or retain.
Please read the cocoa memory management guidelines for more info.
Useful links:
http://www.cocoadev.com/index.pl?MemoryManagement
http://www.cocoadev.com/index.pl?RulesOfThumb
At some point you are either releasing a UITableView instance that you do not own or you are failing to retain one at some point where you keep a reference to it (e.g. you store it in an ivar or a property declared assign rather than retain).
I have written about how to debug things like this on my blog:
http://loufranco.com/blog/files/Understanding-EXC_BAD_ACCESS.html
Basically, try these three things first:
Do a Build an Analyze and fix everything you see
Turn on Zombies, run your code -- it will tell you if you talk to dealloced objects
If that fails, try Debug Malloc, but that's way harder.
I apologize, after re-reading all my source code, I found ONE ViewController (I have around 20 ViewController), where I released an Outlet, in ViewDidUnload.
The reason that it crashed randomly is that I didn't understood well the mechanism of ViewDidUnload, it is called to release views (but not objects of controllers) when memory is low and view is not visible (ex: First ViewController of a NavigationController), and the views are re-loaded when the ViewController become visible again...
In simulator, memory is rarely an issue so ViewDidUnload is almost never called...
Problem fixed, thank you everyone for your help
To help with making sense of the trace, see iOS Debugging Magic (Technical Note TN2239) and Understanding and Analyzing iPhone OS Application Crash Reports (Technical Note TN2151).
Jeff
I have been struggling with this issue for a while and i noticed that many people came across the same thing by reading many posts here and on other forums. Just this morning i realised what i was doing wrong and i thought of sharing it just in case someone stumbles over it in the future.
the problem in my implementation was that within viewDidLoad of view controller (VC1) i was setting its view property to a new view controller (VC2) which forces i believe the framework to exit viewDidLoad of VC1 without reaching its end, hence not calling the consequent delegate function of the view controller: viewWillAppear, viewWillDisappear, viewWillAppear, and viewWillDisappear!
So my solution was to delay all the code that has to do with creating and setting VC2 to be called from within viewDidAppear instead of viewDidLoad. If you do it from viewWillAppear you will get to the same trouble.
Hope it helps
AF
Why would you go to all this bother just to save the memory of a UIViewController?
sizeof(UIViewController) gives 132 bytes. Even knowing that a view controller will create a fair few support objects so it's going to take up more memory than that this is a fantastic example of premature optimization.
I'd give it a fair chance that the code solution you have gone for will :
(a) leak memory in edge cases
(b) fail on further updates to iOS
(c) be a nightmare to debug by any coder other than yourself
(d) be a nightmare to debug by yourself in more than a few weeks
Why not just write your app using the frameworks provided and profile it - if this tiny amount of memory is causing you problems the fine, implement your solution. If not, leave well alone.
Hey all, I'm completely stumped with this iPhone problem.
This is my first time building a view programmatically, without a nib. I can get the view displaying things just fine, but the darn ViewController isn't responding to touches the way it used to in programs where I used a nib. I should add that in the past, I started with the View-Based Application template, and this time I used the Window-Based Application template.
My thinking is that the View-Based template does something magical to let the iPhone know where to send the touch events, but I can't figure out what that would be even after several hours of bumbling around Google. Or I could be looking in an entirely wrong place and my troubles are related to something else entirely. Any thoughts?
There's nothing magical in the view-based template. The most likely reasons for failure to respond to touches are:
You've messed with touchesBegan:withEvent:, userInteractionEnabled, exclusiveTouch or something else, thinking you need to mess with these (generally you don't; the defaults are generally correct)
You created a second UIWindow
You put something over the view (even if it's transparent)
Simplify your code down to just creating a view programatically that responds to a touch and nothing else. It should be just a few lines of code. If you can't get that working, post the code and we'll look at what's going on.
Problem solved. touchesEnded != touchedEnded.
That'll teach me to program without my glasses on.
Another possible scenario for failure in response to touches is when your VC frame is not predefined and its boundaries are actually exceeding the window placeholder. It happens a lot when you just forget to define the frame property for the VC.
Once you define it correctly - User interaction returns to normal.
Good luck !