If I have a service running in the background in my iOS app and someone kills the app (force closes) then the service does not restart automatically (I have not checked that but seems logical). Is there any way to have an app that does not allow the user to kill the service? Or that restarts the service automatically, even if the user kills it?
I do not think that you can, have a look at Apple's documentation.
Some apps are allowed to run in background, see part Background Execution and Multitasking of link above. It depends on what your app will do.
You can still ask for last-minute tasks when you'll enter in background, as you can see in the link above.
But anyway, once you are killed, it's over.
Hope it helps !
Related
I understand that this issue has already been covered extensively in the past, but I'd like to readdress it it appears that there is a lot of mixed messaging around the subject.
I have an application that should be periodically updated, roughly once a day at the minimum, to run some maintenance tasks. I have researched extensively on how to achieve this behaviour, but options such as background fetch and silent push notifications do not appear to work when the app has been terminated (swiped up on) by the user. (see this link for app states)
Will IOS wake up my app if it is in the terminated state, for example, if a user has swiped up on the app? I would like to find a solution that allows me to have the app run in the background in as many circumstances as possible.
What are my options here?
It is not possible to run a terminated app with Swift. Once an app has been terminated, it is no longer running and cannot be restarted. The only way to run the app again is to open it from the device's home screen or app launcher.
There is a crash happen when coming back from background through app icon.
However I cannot see any detail info in console log. There is a signal to terminate, but we cannot find signal number.
<FBApplicationProcess: 0x117bcb930; Maixxxx; pid: 1762> exited abnormally via signal.
Process exited: <FBApplicationProcess: 0x117bcb930; Maixxx; pid: -1> -> <FBApplicationProcessExitContext: 0x17103f820; exitReason: signal; terminationReason: (none)>
The procedures to reproduce my crash is as follow:
Start app through click on app icon.
Use the app as normal user.
Press home to put it in background.
Wait for some minutes.
Click the app icon on springboard screen in order to use it again.
The app crash&exit.
Since the crash only happen when coming back from background, and required to enter background for some minutes, I cannot run in debug mode with lldb attached.
I didn't use any of background features.
Also, I didn't see any crash report in Fabric's Crashlytics. So I think signal handler could not be called neither?
How to investigate this kind of problem?
These things can be tough, I know that from similar experiences. Without knowing more about your app I can only offer hints and no definitive answer, but perhaps this helps you.
The fallback and tedious approach to use direct logging with print and so on notwithstanding there are a two ways to try to "catch" a process.
However, first let me stress that "background" is not always the same and people unfortunately use the term often loosely. Depending on what state transition causes your crash you might run out of luck and have to simply experiment using manual logging. Apps can be in background, i.e. not in the foreground, but still running. This is usually the case when the debugger is attached, otherwise it couldn't do its job. Alternatively they can be suspended (or even terminated) by the OS. The debugger prevents this, which you probably already figured out.
The two things that might help you are:
If you're using background fetch, i.e. "coming back from background mode" as you describe it happens automatically you can activate the "Launch due to a background fetch event" option in your build scheme's "Run" configuration section.
Run your app from the Home screen, put it into background with the Home button and wait a bit (you've probably done so in the past already to get a feeling for when the crash would happen). Your app should eventually go into the suspended state (but you have no way to actually see that anywhere AFAIK). Instead of getting it to the foreground again via the multitasking UI, simply attach the debugger again via the "Debug - Attach to process" menu. This should get your app from the suspended state back into the background state, where the crash probably really happens (if it were to happen when coming from background to foreground you probably would have been able to debug it as usual). Hopefully the debugger has finished attaching to it in time, otherwise I'm out of ideas. :(
I haven't run into this specific problem myself personally, but I know background stuff can be tricky. Maybe this discussion also helps you (I took part of my info from there as well).
Run the app in debug mode on a real device. Press the Home button to send the app to background and continue the debugging. Then you can bring the app to foreground and keep debugging, or put a breakpoint at applicationWillEnterForeground.
You can't debug this on the real device. When the debugger is attached, your apps will never go to background mode in the real device.
You can try to debug this on a simulator.
Anyway please check your class attributes and set attributes to strong to make sure this is not happened by missing attributes.
I have read several StackOverflow questions that have FBApplicationProcess. Usually, this one happened by missing array or something when the app started.
Best regards.
I have gone through all the above answers and all have given proper answers. Though, I would like to share my point of view.
If the app is running on any iOS real device with debug mode and wire plug-in or even on Simulator, App will never go in the background.
If the app is running without wire plug-in or run without Xcode(directly launch the app in iPhone) and then put the app in the background, the app will be running in the background of next 3 mins. After 3 mins, the App will automatically be suspended and removed from the main thread. Now, when we open the app again, It will be considered a fresh launch.
If your app having any Background Capabilities ON, then your app will be alive even in the background, but you can't do any UI changes during that time.
To keep app alive in the background, Background Capabilities must be handled properly. ie. If Location is used in your app with 'While-App is in Foreground' condition, app will not run more than 3 mins in background. So, If you want to run your app continuously in background, you must have to represent proper reason in Info.plist file with Battery drain word, or else, Apple will reject it.
Ping me for more detail on your question.
Thanks.
Crash logs still available on your test device.
To get the crash log try the following steps:
Connect your test device to the Mac through USB.
Launch Xcode. Go to Windows > Devices and Simulators.
Choose your device from the devices section on the left side of the screen.
Select View Device Logs button.
Identify and select the Crash Log to see the contents.
I'm having issues with my WKWebViews'cache being purged sometimes when a user hasn't been using my app for a while.
I guess, that's because iOS puts my app in Suspended and then a low-memory condition occurs so my app is purged.
I read Apple's documentation about The App Life Cycle - Execution States for Apps
Especially the part describing the Suspended state :
Suspended - The app is in the background but is not executing code. The system
moves apps to this state automatically and does not notify them before
doing so. While suspended, an app remains in memory but does not
execute any code. When a low-memory condition occurs, the system may
purge suspended apps without notice to make more space for the
foreground app.
Two questions here :
1) What does "purge" mean exactly ? The app is killed ? Or does it still appear on the app selector ( when double-tapping the home button )
2) Here we can see that there is no way to know when an app is going to be suspended. All right. But if a user comes back to the app, is there a way to know, then, that the app has been suspended ? I can't find any UIAppDelegate's method to do so, but there might be another solution ?
Purge - The purge command forces disk and memory caches to be emptied,
offering a ‘cold disk buffer cache’ which is similar to the state of
the operating system after a reboot.
Referenced from here
As per the documentation
applicationDidEnterBackground:—Lets you know that your app is now
running in the background and may be suspended at any time.
This is the only method which will let you know that method may will enter in Suspended State
also
application:didFinishLaunchingWithOptions: will let you now that
your app's launch process is almost done and the app is almost ready
to run.
The app is in the background but is not executing code
I think it's explained good by Apple, the app is still in memory but no background threads are executed since foreground app requires more resources. Maybe when memory is restored, your app can execute background code again if has not been killed by OS.
When low-memory condition occurs, you're app could be killed (purge).
Is there a way to know, then, that the app has been suspended?
When app is killed from OS, next launch is equal to a complete new restart of app. For this AppDelegate doesn't provide a method to achieve this. You could set a flag in UserDefaults when app goes in background and then make some logic on that flag.
I'm building an iOS app for iOS 8 & 9 and I am facing the problem that when the app goes to background the system is terminating it after just 2 or 3 minutes.
My testing is easy:
I kill all running apps from my iPhone.
I restart my iPhone (to ensure no other apps are taking memory).
I launch my app.
I do nothing inside my app.
I press the "Home" button, moving my app to background.
I wait doing nothing else for 2 or 3 minutes.
I open my app again and surprise, the system has terminated it and now it is restarting as a new launch.
Some comments:
The app does not use CoreLocation in background neither any other service.
I've profiled the app, trying to understand if it is consuming too much memory. When moving to background, it consumes around 25Mb of RAM memory. I'm attaching a screenshot below.
This behavior has been tested on iPhone 5, 5s, 6, 6+.
In iPhone 6s and 6s+ seems to take a bit more time to happen, but still happens.
My question is: Do you know why would this be happening? anything I might not be considering or just forgetting?
I don't want to force my app to run in background by using CoreLocation or something similar. And I'm ok if the system kills my app eventually. What I don't want is that everytime I move my app to background the system terminates it.
Any hint or help will be appreciated.
Thanks,
All applications are automatically killed by the system
According the Apple documentation:
App Termination
Apps must be prepared for termination to happen at any time and should not >wait to save user data or perform other critical tasks. System-initiated >termination is a normal part of an app’s life cycle. The system usually >terminates apps so that it can reclaim memory and make room for other apps >being launched by the user, but the system may also terminate apps that >are misbehaving or not responding to events in a timely manner.
Suspended apps receive no notification when they are terminated; the >system kills the process and reclaims the corresponding memory. If an app >is currently running in the background and not suspended, the system calls >the applicationWillTerminate: of its app delegate prior to termination. >The system does not call this method when the device reboots.
In addition to the system terminating your app, the user can terminate >your app explicitly using the multitasking UI. User-initiated termination >has the same effect as terminating a suspended app. The app’s process is >killed and no notification is sent to the app.
https://developer.apple.com/library/ios/documentation/iPhone/Conceptual/iPhoneOSProgrammingGuide/TheAppLifeCycle/TheAppLifeCycle.html#//apple_ref/doc/uid/TP40007072-CH2-SW1
You can track position but you will certainly see a blue status bar to indicate that an application use GPS tracking.
Maybe you can try to "wake up" your app in background with silent notification...
If it is not necessary to keep your app alive, trust the system...
Some error in inside your code. Please select debug Navigator before run your app... Now you can able to find your error..
Or too much memory also it will terminated..
Apps which are running in the background drain battery life faster, It gives you a bad perception of the device, instead of the app, because the average consumer has no idea that it's an app draining battery.
Thus iOS won't allow your app to run in the background, more than a few seconds. But there are some exception, an app can request extension to this by declaring that its starting a Background Task.
for more info you can check below links:
http://blog.dkaminsky.info/2013/01/27/keep-your-ios-app-running-in-background-forever/
http://www.speirs.org/blog/2012/1/2/misconceptions-about-ios-multitasking.html
I am working on a VOIP app and need it to auto-start when the iPhone starts up. Everything works 80% of the time. But 20% of the time the app fails to startup. One test scenario is the following:
Open app and type something and save
Reboot phone
Check if app is running by double-tapping the home button but DO NOT open the app.
If app is running, reboot phone again and see if the app comes up again in the background process.
This scenarios works most of the time but not always. Other scenarios also fail at times. Can someone clarify if there is a fool-proof way to start a VOIP iOS app every time the phone boots up?
Thanks.
No, it can't be done. If a user force quits an app, it stays force quit. That's how apple want it, and that's how it's going to be. You can't circumvent the users wishes with multitasking. Also, it's worth knowing that what you see in the fast switcher is not necessarily everything that is running, it's what ios thinks the user should expect to be running ie it may shut something down in the background of its own accord in order to free up resources, but because the user did not initiate it this app will appear to still be open in the switcher, despite that it is not.
Sorry, you can't open an app on startup. You should include a reminder on the app's first start up for the user to keep that app open in the background.