Sometimes user moves to other app, i.e. to browser, and when returns to app, app do not show the latest screen, because it seems it has restarted. Is it possible? Users states it happens.
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I’m putting an app into background.
Assuming that I’m not doing anything to keep the app alive in the background, then the app goes through suspended state in a matter of 5 seconds. Right?
What happens if I then tap on the app icon? That’s not suppose to trigger a didFinishLaunch right? It will just bring me back to the last screen I was at and also trigger didbecomeActive & willenterforeground notifications. I won't be getting any other callback. Right?
Assuming there is no restart of the phone, point 2 is true even if there are hours between me tapping home and then tapping back the app icon. Right? Does it also persist device restarts but not force-restart?
The only time I won’t be brought back to the screen I was at (before hitting home) is if the device receives a memory warning and my app is flushed out of suspended state. At this point tapping on the app icon will result in didFinishLaunch. Right?
(I’m asking all of this because sometimes after putting the app in the background and tapping the app icon again (e.g. 10 minutes later), the app is going through it’s launch phase. Most of the time it just goes back to its previous screen)
I've already seen Will ios terminate the app running in background after a specific time? but that doesn't address all aspects I want.
It will just bring me back to the last screen I was at and also trigger didbecomeActive & willenterforeground notifications.
Right, if your app was not terminated in the background.
I won't be getting any other callback.
Not necessarily true. If you were summoned to the front by a local notification, for example, you'll also get an event about that.
Assuming there is no restart of the phone, point 2 is true even if there are hours between me tapping home and then tapping back the app icon.
Not necessarily. The app might well be terminated silently in the background.
Does it also persist device restarts but not force-restart?
Absolutely not. How can the app run when the device is off? Shutting down the app terminates every app.
I’m asking all of this because sometimes after putting the app in the background and tapping the app icon again (e.g. 10 minutes later), the app is going through it’s launch phase
It's not a matter of time. The watchdog process is constantly combing the suspended apps looking for the ones that take up too much memory so that other apps can run. You must not be surprised if yours is one of them.
You can come back to the front launching from scratch or by coming back to life from suspension; it's the most basic fact of iOS app life! You just need to accept it.
But there are lots of things you can do to reduce your chances of being terminated in the background. Giving up memory-consuming objects as you background is first on the list.
I have an app when a specific action fires I close the app and ask the user to reopen it again.
The problem is when the app executes exit(0) the app stays in the apps stack (when I click the home button twice). I want it to be killed completely so that viewDidLoad() will be executed again when the app opens.
You cannot terminate an app on it's own.
From Apple's Human User Guidelines...
Don’t Quit Programmatically
Never quit an iOS application programmatically because people tend to
interpret this as a crash. However, if external circumstances prevent
your application from functioning as intended, you need to tell your
users about the situation and explain what they can do about it.
Depending on how severe the application malfunction is, you have two
choices.
Display an attractive screen that describes the problem and suggests a
correction. A screen provides feedback that reassures users that
there’s nothing wrong with your application. It puts users in control,
letting them decide whether they want to take corrective action and
continue using your application or press the Home button and open a
different application
If only some of your application's features are not working, display
either a screen or an alert when people activate the feature. Display
the alert only when people try to access the feature that isn’t
functioning.
Have a look at this answer: https://stackoverflow.com/a/8491688/742298
I've noticed that when I go off an app like Snapchat, Twitter etc for a few seconds then go back on it, it opens from background as expected, on to the view controller I was last on. However, if I go off the app for more than a few minutes, when I tap on the app it loads the splash screen again and opens the home page.
I initially thought this was standard iOS behaviour, but when I installed my app onto my device I have noticed that even if I go off it for hours, when I come back onto it, the last view controller I was on is shown.
I have thought about checking how long the app was in background by saving times in NSUserDefaults, but don't actually know if this is the right way of going about achieving that kind of behaviour?
Thanks!
We're seeing a strange situation on our iOS app that is impacting our user experience.
When a user background's the app (by pressing the Home button), we can clearly see the app entering the background. When the user then force-closes the app (by double-tappinging the Home button and sliding-up on the app), the app terminates normally. When the app is then re-opened, it follows the normal iOS start-up sequencing.
However, if the user double-taps the Home button while the app is running (resigning the app from active, but not sending it to background) and then force-closes the app (by sliding-up on the app), we're seeing the app terminate (the process gets killed), but then the app immediately re-starts in the background (with a new pid). The app is not designed to start-up or run in the background, and this is causing UX issues.
The app has no entitlements to run in the background, although we do have a couple of third-party libraries that have tasks that wind-down when the app enters the background.
I suspect the issue is a result of the app being force-closed from a non-active state rather than a background-state. If the app enters the background first, the third-party tasks are getting a chance to complete. If the app is force-closed from the non-active state, the tasks never get a change to complete in the background, so iOS is restarting the app in background to give those tasks a change to finish. It's unclear, however, if this is correct behavior.
-Stix
I'm kinda thinking the questions were self-evident, but if not:
Is this correct behavior for iOS? Should iOS be restarting the app in the background when the user force-closes the app w/o putting it into background?
If this is correct behavior, what can cause this to occur? Is it possible some third-party framework - still running a background task that hasn't completed - is the culprit?
The force-close works fine if the app is put into background first (giving background tasks the ability to complete/expire). Is there anyway to force it into background when force-closing the app while it's in a non-active state?
Very difficult issue to figure out...this only happens on a real device not plugged in. When my app loads up to the main view, i show a wait dialog while a few background threads fire off and search for products. this takes about 5-7 seconds. If I load the app and about 1-3 seconds in, i close the app and go to another app, then come back to my app, the screen dims around the edges and the app just freezes.
I did a few google searches for this screen dimming and couldn't find anything
The app never crashes.