I am facing very strange problem in my app. My app is getting killed when I keep my app in background for long time. I have checked the memory usage of the app in the 'instruments' tool, the live memory usage of the app was 1.48mb and overall usage was 6.18mb, which is not very high. Still my is getting killed.
I have checked my app even if there are few apps running in background say around 4 still it's killing my app. What might be the reason for this?
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I have a map based and location based app which I put into the background. I then start a a game app (agent dash) after the game app has finished initializing I noticed that my app has been killed: 9 in the device log. Sometimes I get a memory warning message, sometimes not. But is it possible for one app to cause another to be terminated. If I run the my app on its own there is no problem. I run other apps in the foreground and no problem. Also if an app can cause mine to be terminated can I generate a restart? Thanks
Agent dash must be an memory intensive app, so when the iOS feels its running out of memory it generates memory warnings which each app needs to handle. It can even kill your app if it needs more memory. The primary thing iOS takes into consideration is that it wants to keep the app which the user is using alive. And no you can't restart your app pro grammatically the user will have to do it if he wants to.
When I press the home button my app is suspended correctly, however it only lasts a few minutes. If I leave it for a short while and return to it the app starts up fresh.
I'm not running any background tasks in my app and other apps stay suspended for much, much longer than mine.
What could be the potential causes of this? Is it likely I have operations running in the background that I'm not aware of and iOS is killing my app when it is short on memory?
The apps that are using the most memory are terminated first in the background. So the likely cause is that your app is consuming more memory than you think it is. I'd start with ensuring that your memory is being managed correctly.
Apple - App States and Multitasking
I've been surprised that iOS 5.1 does not manage memory quite as I expected. When the device is running a lot of apps, it appears that iOS does not kill memory hogging apps in the background, but sends memory warning to my own app as well.
For example showing a UIImagePicker crashed the app on two test devices. Double tapping the home key and killing some of the background apps prevents the app from receiving the memory warning and crashing.
I'm wandering if iOS would not free up memory for me, is it acceptable to show some sort of alert view notifying the user that the memory is low and some of the background tasks have to be killed?
I'm at a loss of how to deal with such events - does it take time for iOS to clean up some memory (while apps respond to memory warnings)?
iOS does a lot of stuff before bothering you with memory warnings, including killing backgrounded Apps. Since iOS 5, iOS is even going to annoy you as less as possible with memory warnings, meaning that you only get one if there really is a need for you to get rid of stuff that is using memory but not needed right now (and that you can safely recreate in the future without taking hours for it). If your App crashes without giving you a memory warning first, chances are that you allocated so much memory that the system can't tell you that its running out of memory before it decides to kill you, the reason for this is that the memory warning is scheduled on the runloop of the main thread and until you give the runloop time to do another iteration, you won't receive the warning.
Also, Apple doesn't like you to tell the user that there is a memory problem; Its your App that has to deal with it, not the user! So its very very likewise that your App gets rejected if a memory warning comes up while the review team is reviewing your app (rumor says that they send these warnings to test how your App reacts to them)
Soo, to sum it up: iOS does work like you expected by killing what it can and even shutting down other system daemons, only after this happening you will be notified that memory is low. The correct way to respond to these warnings is to free up as much memory as you can, start with the big stuff that can be easily recreated in the future (eg. if your app shows loads of pictures but not all are visible at a time, throw away the ones that aren't visible right now). Telling the user is the wrong way to deal with the problem and Apple doesn't like it, so try to solve the problem on your end.
I have an iPhone application I'm testing - I've just noted when testing it on a device that sometimes when I resume it (i.e. launch it again in the "multitasking" sense when I expect it to appear and continue on) the startup image appears. As if it totally restarted.
Would this be an indication of memory issue with the app?
Good question. I've noticed this as well and wondered also. It might not be this app that has an issue though, but other apps have required extra memory which caused the system to take memory from this app. Im not sure exactly because (if I recall correctly) the resumed app restarts on the screens it was on, so it didnt lose state. I wonder if in this case, iOS has unloaded some of the backgrounded task's code and its taking a bit of time to read the code back in, so it puts that screen up. However, if this was the case, then the app would really need to be idle and not active in the background.
I recently had an app rejected from the app store because of Low Memory Exception. The app doesn't leak memory, but its base memory footprint seems to be too high. According to the crash logs sent by apple, it was taking about 14000 pages in the memory (mostly due to huge textures). There were 2 strange things though:
I tested it on 5 devices rigorously before submitting, and never got this crash on any one of them.
I did optimize the textures after the rejection, and brought them to about half the original size (texture memory consumption).
I have no way of knowing how many pages my app is taking now, unless I can reproduce the same crash as apple (which I never could). Is there another way to be able to find out the memory footprint of my app, so that I can be sure that it is optimized enough now.
I did try instruments, but my app crashes when I try to run it through my XCode (must be some problem with my XCode). But it works perfectly when I run it directly on my iPhones/iPods. Any help in finding out the memory footprint of my app on iPhone (if there is something analogous to task manager of windows), would be appreciated.
Thanks
EDIT:
Launching the app from XCode gives the following error in the console:
"Error launching remote program: failed to get the task for process 553."
Launching the app with Activity Monitor gives the following error:
"Target terminated too early to collect data"
EDIT2:
I was able to run my app with Activity Monitor, by using a dev profile instead of distribution profile. But now there are several sections in the Activity Monitor - Physical Memory Used, Real Memory, Virtual Memory. Which one of these do I consider. To sum it up, I need to know which one of these causes the iPhone to throw a Low Memory exception.
XCode -> Run -> Run With Performance Tool -> Activity Monitor.
If the device is connected, Activity Monitor runs on the iPhone/iTouch.
I think you're coming at this from the wrong angle. You're asking how to find the memory footprint without using XCode. I think the question you should be asking is: why can you not use XCode? Presumably that's what you used to develop the application in the first place?
Without XCode you're pretty much flying blind. You say you halved the size of your textures, but how do you know? Does your app release any extraneous memory when it gets a low memory warning? (applicationDidReceiveMemoryWarning:)
First, have you looked at the crash logs from when you run your app from XCode? You should be able to see them in the Organiser in XCode.
I'm not sure there's a single solution to stop your app crashing with XCode. Normally when my iPhone won't allow debugging I just restart xCode and my handset and it starts working again. Restarting XCode sometimes helps. I would also try reinstalling both XCode and the iPhone SDK.