I need my iPhone app to do some tasks in the background when it's suspended, but I don't need to do any tasks after it's turned off. Do I need to settle UIBackgroundMode?
Yes, to execute code continuously in the background state, you need to register for a given UIBackgroundMode.
See here or here for a good source on this.
However if you just wish to perform a single background task (task completion), you don't need a background mode.
In response to your comment below, I will try to be clear:
In iOS, even in iOS 7, it's not possible to run arbitrary code when your application is in a background state indefinitely.
In simple English, - you can't just run any code you like in the background for as long as you like.
There are rules.
These rules have been relaxed somewhat in iOS 7, but it's still not totally unrestricted.
Consider your situation: You have a timer that wants to call a method on a continuous basis.
Now consider the UIBackgroundModes available (which allow you to run in the background in various situations):
audio - Only for audio based apps.
location - Only if you app is location aware, does specific location tasks
voip - VOIP (Skype etc)
fetch (Background fetch - a new iOS 7 API where the system gives you application moments to grab new content when it sees fit.
remote-notification - new in iOS 7, when the device receives a remote push notification with a certain payload, it will resume and execute a certain block of code.
newsstand-content - Only for newsstand apps
external-accessory - Only for external accessories to communicate with the device
bluetooth-peripheral Only for external BT accessories to communicate with the device (fitbit)
As you can see if you don't fall into one of these categories you can't use these modes.
If you misuse the modes Apple won't approve your application.
Finally we have 'Background task completion'
This is a way to use a UIBackgroundTask to execute any code you want in the background! Including timers that call methods! - One problem though...
This is supposed to be for 'task completion' (Facebook uploads that aren't complete, saving or processing data that should be done before the app suspends even though the user pressed the home button).
Sounds good, but you can only run in the background using this method for a maximum of 10 minutes. If you go over this time limit iOS will immediately kill your application.
So as you can see, there is no way for your application to be approved on the store and constantly run in the background with a timer that calls your method.
Sorry about that.
If you want to learn more check this out.
Use the location service and set NO location manager "pausesLocationUpdatesAutomatically" property.
Related
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.
I want my iOS apps to run continuously in background 24/7
I tried many options like background location updated with background task expiration handler, but later after some times it seems that the application gets suspended in background and user is brought back to the root view controller.
Any help will be appreciated.
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 record audio content while in the background
Ap ps 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
Apps that implement these services must declare the services they support and use system frameworks to implement the relevant aspects of those services.
Declaring the services lets the system know which services you use, but in some cases it is the system frameworks that actually prevent your application from being suspended.
You should read this page of Apple Programming Guide : Background Execution
It is not allowed to run background tasks 24/7. But you can use many different ways.
You simply can't. Apple don't give any mean for an app to ensure background execution. iOS will give you processing time whenever it feel like it, and you cannot control that.
In my application I need to log user status every 15 minutes. Is it possible if the app is in background (not killed)??
Currently I enables the Background location update. But how to call in each and every 15 minutes
While other answers are correct about background fetch, there is also another background option called VoIP, which apps like Skype use. In this case OS will wake up your application more frequently (even every 10 minutes if I remember correctly) and you can keep pinging your server in background. The obvious down side is that your app must have Voice over IP functionality, otherwise it would get rejected on the App Store.
All you need to do is add call setKeepAliveTimeout:handler: method and have voip enabled in background capabilities.
Just adding this for the sake of completion.
You may want to look at the Background Fetch capabilities added in iOS7 and beyond:
http://www.appcoda.com/ios7-background-fetch-programming/
https://developer.apple.com/library/ios/documentation/iPhone/Conceptual/iPhoneOSProgrammingGuide/BackgroundExecution/BackgroundExecution.html (Search for background fetch)
You won't be able to control the interval to exactly 15 minutes but you will find that this mechanism is the closest Apple will allow.
It is not possible to perform network calls at clearly specified intervals when your app is in background mode. You can tell your app to use background fetches
This article gives a great overview on the capabilities that you can do with this API. Basically it allows you to tell iOS that your app wants to perform networking calls in the background, however you can't exactly control when and how often iOS the network calls are going to be performed. iOS will schedule your network calls for you, and depending on how your app is used it will adopt the frequency with which it performs the requests. Documentation can be found here.
How does Navita https://itunes.apple.com/us/app/navita-t.e.m.-personal/id590228620?mt=8
manage to display a call log?
If I swipe the app out of the task manager then it misses the calls, this indicates that it must presumably be using CTCallCenter's callEventHandler and is creating its own call log by saving the time/duration in response to the callEventHandler callbacks.
However if that is the case then how does it manage to do this in the background? I was under the impression that callEventHandler can only be used by apps in the foreground and not in the background?
The app is using location services, however even after disabling this it was still able to get information about the calls (provided the app isn't suspended). I though it might be using background location updates to keep itself primed to receive callEventHandler callbacks but apparently not.
The Navita app is additionally able to display call time and call duration.
The bounty will be awarded to an answer which contains sufficient, accurate and detailed information that enables me to emulate the behavior of the Navita app, specifically I must be able to write an app that can obtain the time and duration of a phone call that occurred while the app was not in the foreground, while the device's location services was turned off, and after the app had been in the background longer than the ~3 minutes granted by using beginBackgroundTaskWithExpirationHandler:
Here is what I observe with the Navita app that I want to be able to reproduce:
1) Run app
2) Task away from app
3) Go to device settings, privacy, and turn off Location Services.
4) Go to device settings, privacy, background app refresh and turn off for the app
5) Wait > 10 minutes to make sure the app is not still in the background as a consequence of using beginBackgroundTaskWithExpirationHandler:
6) Call the device from another phone, answer the phone call, then hang up.
7) Launch the app again and display the call time and duration
(This is iOS7 and unjailbroken)
Here is what I've found from Navita TEM disassembly and it's resources.
Application uses two background modes - location and audio. You can see it in the Info.plist file. When you enable phone calls logging application will also enable "alerts" and "Real-time" switches. When "alerts" enabled application infinitely loops in background "bg-sound.mp3" file which has no sound, it's just silence. Because of that it doesn't use hacks like this one How to get a call event using CTCallCenter:setCallEventHandler: that occurred while the app was suspended? . It's similar trick to location used in order to keep the app running in background and receive phone call events. Somehow this was not rejected from the AppStore.
If you are observing the call center while the app is in the background you get a set of updates when the app is brought back to the foreground. This set of data may not be as accurate as if the app had been mostly in the foreground but it does include quite a bit of info.
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