I am trying to test an application that needs to run over an extended period of time and to aid initial testing I am trying to find a way to stop iOS moving the application to the background and suspending it. Ultimately I will add code to facilitate the use of multi-tasking but right now I just want to better test the core mechanics without iOS pushing it into the background all the time.
You can not prevent ios from suspending an app. The home button will close/resign active the application and even if you request for a background task apple can kill your app at any time as it sees necessary (More than likely for memory reasons).
As long as you, the user, don't stop this app, launch another app, or lock the device:
[[UIApplication sharedApplication] setIdleTimerDisabled: YES];
might keep your app running in the foreground. Don't forget to re-enable the idle timer, or this could keep the device running until the battery is dead.
Related
I used NSTimer to call a method after 1 sec when app goes in background and after nearly 17 minutes timer stops working.
When it came back in the foregound it again started working, so please tell me why this is happening and how to resolve the issue.
I also tried using perform selector with delay in recursion for the same purpose, but again giving the same result. Please suggest any solution. Any help will be completely appreciated.
Wierd issue- i too had this one, but the following worked for me.
//Run the timer on the runloop to ensure that it works when app is in background
[[NSRunLoop currentRunLoop]addTimer:self.timer forMode: NSDefaultRunLoopMode];
From 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
If few minutes isn't enough, you can't make an app run infinite time in backgorund unless it uses:
Audio Playback
Location Services
External Accessory
You can use Background Tasks to get 10 minutes of running time for all other apps, or Local Notifications to notify user.
While the device is powered on, is it possible for iOS to automatically terminate my app (calling applicationWillTerminate:) while it's in the background?
I'm also curious what happens in two other cases, three in total:
Device is powered on
Device is powered off
Device loses battery
I'm asking because I want to know how often applicationWillTerminate: is likely to get called. I want to know this because that's where I'm registering for remote notifications. And if there's a failure sending the device token to the server, I want to know how likely it is that that method will get called again (i.e., retry sending the device token to the server).
If your application supports multitasking (the default for anything linked against iOS 4.0+), this method will almost never be called. The documentation says it may be called in cases where the application is running in the background and the system wants to terminate. However, in my experience, I've only ever seen this actually called when running a music app that's actively playing music in the background and the system is jettisoning everything. In cases where I have background tasks running (not music, but short-term background tasks), I've seen the app terminated without this method being called.
I wouldn't ever rely on this being called and try and do all the clean-up you need to do in your delegate methods for transitioning into the background and your background task completion blocks (which do get executed for at least a few seconds before the app gets jettisoned).
Not only can iOS terminate your app automatically, but the user can kill it manually. In fact, the only time the user can kill your app is when it's in the background. Furthermore, when your app is "in the background" it's more likely to be suspended than actually running, so don't count on doing a lot of processing when you're not the foreground app.
As for how likely it is that you'll get -applicationWillTerminate:, that'll depend on the user and how they're using their device. You should handle it appropriately when you get it, and go about your business otherwise.
When memory is running low, iOS can shut down your app, calling applicationWillTerminate.
The docs say this about the method:
... However, this method may be called in situations where the application is running in the background (not suspended) and the system needs to terminate it for some reason.
Check out iOS Developer Library : iOS App Programming Guide : App Termination.
I want to update my sqlite database in my iPhone app in every 2 hrs from the server.
Is there any way to call web services from the background even the app is not active?
You can't do this. The best you can do is sync when the app starts up. And if its backgrounded, you wait until they bring it to the foreground and can sync if it's been longer than 2 hours since the app was last in the foreground.
Apple won't let you do these battery draining and CPU stealing things. And really, you don't even need to. If your app isn't using the data, then it doesn't need to be up to date.
You can't run your app in background for doing this. You're app is only allows to run in background for doing Audio Playback, VoIP and Task Completion (till 10min after going to background). But you could do the update once in 2hours when the user starts the app? doing something with push notification to inform the user? But you can't just run something every two hours in background.
I am developing an iphone application and I think that it's business logic requires a service to be always running in background.
The service needed is to get the acceleration of the device and notify or perform a certain action when that acceleration becomes a certain value.
Is that allowable in the Apple policies, or is there any idea about a solution?
What cydia development possibilities to help me ?
Dbramhall left out one important thing:
You can't guarantee that your app won't be killed, the OS can kill apps that are in the background at will if it requires more memory.
So if at all possible i wouldn't rely on making sure it can run its process in the background and before you ask "How can i stop this?". Well you shouldn't I've never tried it myself because i don't know the effects it has on the OS.
Also if you stop it from being killed in the Background, if it is going to be on the app store then it won't pass evaluation process, because it breaks the OS
Well, an application can run in the background and Apple perfectly accepts this however the user will obviously be be able to close the application (or should be able to) via the multi-tasking bar and this will end the application. Period.
Apple will not accept an application that runs constantly regardless of whether the user has is in background state as this drains the battery, heats the device etc. So an application can run in the background so long as the user can quit it when close it from the multi-tasking bar however it cannot continue to run after the user closed it via multi-tasking - if it does continue, Apple will reject the application.
Also, see 2.16 of the Apple Store review guidelines: https://developer.apple.com/appstore/resources/approval/guidelines.html#functionality
I have noticed that some apps e.g. Skype run in the background.
I would like to have my app run in the background also, waking up every 1 seconds to update some data and then going to sleep again.
How can I do this?
I gather that NSTimer's do not work in the background.
You can't. Voice-over-IP apps get a special exception for this, basically the system manages a network socket for them and wakes them up if there's data. There's no way to do the same with a timer.
By the way, waking your app every second, your battery wouldn't last half a day.
See Executing Code in the Background
You would need to use push notifications to push information to the app (like the Facebook or Skype app). See this documentation from Apple on how to use push notifications.
Not every second though, that would drain the battery. Other than that, there isn't really a way unless you are running a VoIP app.