I am facing the above issue and unsure why it is happening or how to fix it. When the app goes to the background and is later reopened, it always starts from the initial view.
I would like it to show the view that was shown when the app was dismissed - which is usually the default for iOS apps.
Can someone please explain why this might be happening and how I can resolve it.
Your app is probably killed while in the background to free it's resources for other tasks.
If applicable you can opt to use a background mode for your app so it keeps running in the background. This is possible if you require location updates, play audio or interact with bluetooth le devices.
By your description it's more likely you want to implement State preservation and Restoration (Programmig Guide)
Even if your app supports background execution, it cannot run forever. At some point, the system might need to terminate your app to free up memory for the current foreground app. However, the user should never have to care if an app is already running or was terminated. [...]
The state preservation system in UIKit provides a simple but flexible infrastructure for preserving and restoring the state of your app’s view controllers and views.
If you are on an iPhone older that the 3GS, this is normal. Apps are closed instead of backgrounded on these older models.
The other possible reason is that you've set
UIApplicationExitsOnSuspend=YES
in your Info.plist. In that case, your app will also always terminate when going to the background.
Related
If I send my app to background by clicking the home button and wait a certain time (perhaps 1 or 2 hours).
What will happen if i tap on the app icon now?
Will the app relaunch or simply be brought from background to foreground?
Quick "prologue":
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Answer:
This question has no definite answer, because it depends. When you tap the home button your app enters, as you've said, the background and is still running to a certain degree. However after done so, the apps life cycle is up to iOS (the devices operating system) to determine. iOS controls and checks memory and CPU usage (etc..) of the device, and if you start another activity while your app is in the background that makes the available memory and CPU etc of the device not sufficient, iOS will terminate any apps in the background to not waste those resources (or battery etc). If so your app will relaunch next time you tap on it.
Although if you don't do anything performance heavy it is more likely that iOS keeps your device running in the background.
I'm not sure about the exact conditions and such the iOS works on, but i would say its very likely your app will have gotten terminated and is relaunched after 1 or 2 hours "in the background". Additional conditions apply if the device is locked during that period.
For proper documentation of this i would recommend reading Apples documentation for handling App State Transitions and/or the api for UIApplicationDelegate on apples developer website. Where you can see what the different methods in the AppDelegate does and how they interact.
Edit (answer to comment):
A way to relaunch the app everytime it goes into background?
Hm, yes, but also no. I'm not 100% sure about this (never encountered that "wish" before), but you can do this in your AppDelegate: (It will basically crash your app, but beware that apple does not encourage you to crash your own app anywhere). Doing this might stop the app from passing through apple store review process (i.e. your app might not be accepted to the App Store).
func applicationDidEnterBackground(_ application: UIApplication) {
exit(0)
}
Check out the answer to these post for a bit more information: call exit(0) in iphone app , objc - Proper way to exit iPhone application?.
Personally I would recommend you to work around it and don't do this. Also remember that when your app will enter the background applicationWillResignActive will be called and when the user opens it again, applicationDidBecomeActive gets called so you can do a reload or something from there if you want to refresh any data.
Whenever we press the home button in our device, the application releases the currently being used memory and moves to background stage. However, when we press this application app icon again it brings the app on top of the iPhone screen and occupies memory again. This is definitely not the relaunch because relaunch depends upon the UIApplicationDelegate method
didFinishLaunchingWithOptions. When we are switching app from background to foreground then applicationWillEnterForeground method fires.
For better understanding, the following link might be useful
iOS Application Life Cycle
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?
I am in the middle of development of an iOS OpenGL based game. So far I was not very concerned with the app states change and life cycle - background, foreground, suspended, terminated etc. Now I wanted to add support to moving the app into a suspended mode (after pressing home) and then nicely recuperate it after restarting it.
My problem is that after pressing home button, the app always gets terminated (the application delegate always reaches -applicationWillTerminate:)
The documentation mentions that in order to prevent termination it is important to clear as much memory as possible, stop any timers etc. Doing this did not help to prevent termination, so I tried to experimentally copy the app delegate form an Xcode template app, with completely NO initialization of my app objects after launch/activation, no storyboard, nothing special in main.m.
While the template (I used an Xcode game template) is never terminated after pressing home, it ends at -applicationDidEnterBackground:, my app despite of the fact that is uses less memory and starts completely no tasks is always terminated.
What may be the reason. Included but inactive frameworks ? I have no clue.
I am trying to force my app to automatically enter the "Suspended" state programmatically, so I can do testing on Core Bluetooth restoration.
I have tried calling
[[UIApplication sharedApplication] performSelector:#selector(suspend)];
but this merely sends it into the background. Am I doing it wrong? Is there a better way? Or is it impossible?
I would like to remind everyone exactly what it means to have an app be suspended, as there is always confusion on the terminology:
(source: apple.com)
An app in the background will get indefinitely suspended if the system needs memory, but Core Bluetooth's restoration can send an app back into the background state temporarily.
I don't know how to do this programmatically, but what I do is to press the home button, then launch a number of heavyweight apps like Safari and graphics-intensive games. The memory pressure causes the system to terminate your app pretty quickly. Core Bluetooth should then initiate the restore process and re-launch your app when it detects activity from a peripheral you are connected to/have asked to connect to.
First of all I hope don't repeat any topic, I have spent a lot of time reading on internet about this before ask.
I'm developing an app for iOS => 5 and I need get the user location, but I don't need always a great accurate position, so when the app goes to background I change the normal location mode to Significant Location Changes and when the app come to foreground I stop the significant location change mode and get back the normal location mode, that's all goes fine,
my problem is when the app goes to background mode or even the user KILL the app the GPS signal (the purple arrow) still appear ALWAYS, even after restart the device, the only way to make disappear it is un-installing the or disabling the significant location changes when the app goes to background, but I need this mode working when the user goes to background mode, maybe not when the app is killed.
I don't know how to stop the service when the user kill the app... because event "applicationWillTerminate" is not called if you have multitask ON.
My main reason because I don't want the purple arrow appear always, even the app is killed is because I don't want the user think the app is drying the battery... so the user won't want the app installed.
First question: Is normal that the purple arrow appear always, even the app is killed if the Significant location change is enabled for the app?
Second question: Is any way to change this, to stop the service at least when the app is killed to hide the purple arrow?
Thank you all.
Sorry for my english if something is wrong.
After few days researching to be sure about this service, seems like there is NO way to use significant locations change in the background without the arrow in the top bar. I have been testing with different apps and reading through internet and nothing to solve this.
The only ""way to solve"" this is disable multitask mode in the app and disable the significant locations change in the event "applicationWillTerminate" but don't make sense... I'm losing the background location always not only when the app is killed... so is not useful.
It's bad... is a really good service to get locations saving battery but as user and developer I don't want an app that make appear this icon ALWAYS even after the app is killed, as developer I don't want that people uninstall the app for this reason and as normal user I don't know what mean this icon if is normal GPS or Significant locations change and what mean this... if my battery is being drain or not.
The other option to get locations in background task but has a big impact over the battery....
I hope apple fix this in future versions... adding at least a new arrow or showing only when a new location arrive instad of always or allowing to stooped when the app is killed.
All this has been researched over iOS - 6.1
Thanks to all.
When you use the significant location change service, the OS keeps your app running. If the app is in the background and is killed, the OS restarts it, so the purple arrow will always show. When a new location is detected, the app is restarted. From the docs:
If you leave this service running and your app is subsequently suspended or terminated, the service automatically wakes up your app when new location data arrives. At wake-up time, your app is put into the background and given a small amount of time to process the location data. ... To stop the significant change location service, call the stopMonitoringSignificantLocationChanges method.
Hmmm, interesting. I've just seen that problem with another app - seeing the arrow still active made me want to disable location updates for that app so the problem is real. Best thing I can think of is to have some kind of timer to disable the location monitoring after a certain amount of time if that is appropriate for your app.