I want to start some process in background mode on timer event.i want to know that is it possible to get start any process in background or terminated apps on timer event,if i set timer for Five minuets and close the app not even running in background mode than after five min process should start automatically, is it possible in iOS?
I have read my Documents and also tried out this Scenario, I have concluded that Apple doesn't provide any background Process while app is terminated excluding Push Notification.
If you want to run any background process then app must be active in background.
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I'm new to iOS development and I'm using Swift in my current project.
I'm trying to achieve something similar I did in Android. I'm trying to run a background service when the app is closed/minimised that will get executed every 2 seconds to keep the user informed that the app is still running in the background and checking for status with the server.
How can I achieve that? I've tried using the "background fetch" method but it doesn't get executed every 2 seconds.
The background service will run no longer than 5 minutes if it matters.
No you can't do that. What you can do is, call a service in applicationDidEnterBackground that lets your server know that your app is in background or killed(You will get very less time for this to get executed, approx. 3-5 sec.).
An Android app like the one you described will likely drain the device’s battery prematurely. This is the simple reason why Apple has restricted background execution to a clearly defined set of tasks:
Apps that play audible content to the user while in the background, such as a music player app
Apps that record audio content while in the background
Apps that keep users informed of their location at all times, such as a navigation app
Apps that support Voice over Internet Protocol (VoIP)
Apps that need to download and process new content regularly
Apps that receive regular updates from external accessories
This list is taken from Apple’s official description of background tasks: Background Execution.
Is there anyway to run background task on iOS? Like periodically checking some system condition of the phone and report on the widget?
Also, I found that if the iPhone is shut down, then those background task cannot execute again when the phone restart.
The short answer: No.
The long answer is more nuanced, but you shouldn't do it anyway. You can schedule your application for background refresh, but that is unreliable (app will not be run on constant intervals), and if user swipes the app in task switcher, the app will not run at all in the background. Another hacky way is to have a server send a silent push to wake the app more reliably. However this is still not guaranteed to succeed; if user swipes the app in task switcher, your app will not run.
In either case, you cannot trigger widget updates from your app. Widget lifetime is managed by the operating system. Instead, implement widgetPerformUpdate(completionHandler:) and perform your widget updates there. However, as above, this is not a periodic operation.
Before asking a question, let me clarify what I understand about iOS App states:
Backgrounded: In this state, your app is not in the foreground anymore but it is still able to run code.
Suspended: Your app enters this state when it’s no longer able to run code.
Now, I wanted to keep downloading going on when App is in background, i.e. it still does exist in multitasking screen. It is working as expected with background transfer service.
But, in some tutorial reference, I have read that you can perform downloading even when App is Backgrounded / Suspended. Can it work even when my App is suspended, i.e. removed from multitasking screen ?
I have been reading many documents including Apple class reference regarding background transfer service with download task, but no one clarifies that the download will not work when App is suspended (killed).
Appreciate your thoughts and advices !!!
If your app has been suspended by the system (without force quiting from multitasking screen) your background session will continue to work.
If you force quit the application all download tasks will be canceled.
The following is from backgroundSessionConfigurationWithIdentifier(_:) documentation :
If an iOS app is terminated by the system and relaunched, the app can use the same identifier to create a new configuration object and session and retrieve the status of transfers that were in progress at the time of termination. This behavior applies only for normal termination of the app by the system. If the user terminates the app from the multitasking screen, the system cancels all of the session’s background transfers. In addition, the system does not automatically relaunch apps that were force quit by the user. The user must explicitly relaunch the app before transfers can begin again.
Apps displayed in the multitasking UI aren’t necessarily executing code or fetching data. Listed apps may be suspended or not running at all
[[UIApplication sharedApplication] applicationState] will check your application state, you can test your app.
NSURLSession class can hand off downloads and uploads to the operating system when the app becomes inactive. As with almost all background execution APIs, if the user force quits from the multitasking UI, the background operation will terminate
In iOS 7, Apple added support for background fetch—a kind of smart, per-app crontab that wakes up at opportunistic times. There is no way to force background fetches to execute at exact intervals. iOS checks how much data and battery power was used during previous background fetches when scheduling future callbacks.
Background fetches can also be triggered by remote push notification and have a very similar delegate method with the same completion handler.
Full Tutorial is here
https://blog.newrelic.com/2016/01/13/ios9-background-execution/
My application runs in the Background (getting location updates) which I need to push to my server for every 10 seconds.
I have scheduled a timer which invokes a function in which the current location updates are captured and pushed to the server. This is running smoothly if the app is there in the foreground. When the app is moved to the background this functionality is running for 15 minutes after which I cannot see the method being invoked at all.
I know if an application is put into background it will be put into suspended state at any time. Also if another app running in the foreground requires memory at that time iOS may terminate some applications in the background. But in my case no application is running in the foreground as I have locked my device.
I also have an idea about expirationHandler. Would like to know if I can keep calling the function in the background without my app going into suspended state and Apple should accept that.
Any suggestions are welcome.
You can add App registers for location updates under Required background modes in your plist.
The same scenario was also in my application i have set the uibackground mode in plist file and use that service from appdeligate and apple approved that application :)
Hope it may help you.
I was trying to run some services in the background so I struck the control in the background by using a while(1) loop in the background delegate for some time.
On the emulator it is working fine but on transfering it to my iPad, the app is crashing after going into the background.
Does the while(1) loop not work for on the device?
On emulator it is working fine but on transfering it to the Ipad device , the app is getting crashed after going in to the background.
If I interpret correctly this that you are writing, what I think is that your app gets killed on iOS devices simply because you are not allowed, except in a few spare cases, to run a thread in your app when the app is "in background" (i.e., after the user has "quit" it by clicking on the home button).
So, if I am right in my reading what is happening, either your app is in a specific class of
apps (see later), or the only thing you can do is "registering" a background thread to run for a limited amount of time after the app goes in the background.
Excerpt from Background Execution and Multitasking
Most apps are moved to the suspended state shortly after entering the background. Only apps that provide important services to the user are allowed to continue running for any amount of time.
As much as possible, you are encouraged to avoid executing in the background and let your app be suspended. If you find you need to perform background tasks, here are some guidelines for when that is appropriate:
You need to implement at least one of several specific user services.
You need to perform a single finite-length task.
You might be especially interested in the "Implementing Long-Running Background Tasks":
For tasks that require more execution time to implement, you must request specific permissions to run them in the background without their being suspended. In iOS, only specific app types are allowed to run in the background:
Apps that play audible content to the user while in the background, such as a music player app
Apps that keep users informed of their location at all times, such as a navigation app
Apps that support Voice over Internet Protocol (VoIP)
Newsstand apps that need to download and process new content
Apps that receive regular updates from external accessories