What is the proper way to handle background tasks in iOS - ios

I have a voip app and it needs to run in the background. To my understanding these are the things I need to do:
Flag the app as voip.
Set the 'application does not run in background' flag to NO.
Set an expiration handler, a piece of code that extends the standard 10 minutes of execution time you get.
More?
I set both flags in the info.plist file and I get my 10 minutes. I tried what is suggested in this post. Here is my code:
//in didFinishLaunchingWithOptions:
expirationHandler = ^{
NSLog(#"ending background task");
[[UIApplication sharedApplication] endBackgroundTask:bgTask];
NSLog(#"restarting background task");
bgTask = UIBackgroundTaskInvalid;
bgTask = [[UIApplication sharedApplication] beginBackgroundTaskWithExpirationHandler:expirationHandler];
NSLog(#"finished running background task");
};
//in applicationDidEnterBackground
NSLog(#"entering background mode");
bgTask = UIBackgroundTaskInvalid;
bgTask = [[UIApplication sharedApplication] beginBackgroundTaskWithExpirationHandler:expirationHandler];
// Start the long-running task and return immediately.
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
// inform others to stop tasks, if you like
[[NSNotificationCenter defaultCenter] postNotificationName:#"MyApplicationEntersBackground" object:self];
//this while loop is just here for testing
inBackground = true;
while (inBackground) {
NSLog(#"stayin alive!!"); //this keeps going forever
sleep(10);
}
});
The situation:
I use a third party library that handles the communication with our webservice. The service is a CommuniGate pro server. I receive presence updates (online/offline) and instant messages from contacts via the library. The library is CommuniGate's ximss library, a protocol they made which is similar to xmpp and is used for xml-based sip requests, as well as IM and presence. When the user logs in to the app, he sees his contacts (CmmuniGate friends list) and he can choose to call one. After a ximss verification message has been sent and the other side accepted the call it logs the start time of the call and starts a facetime call.
The problem:
When the app enters the background by pressing the home button, I start seeing the 'stayin alive' message in the log and every ten minutes I see that it restarts the background task.
When the app enters the background by pressing the power button, the 'staying alive' messages start showing up for ten minutes, after that it restarts the background task and start restarting it about every 50-100 miliseconds.
I would've been fine with this for now, even it eats battery, because I have time to work on updates and our users don't own the ipads, we do. The problem for me now is that the ximss library loses it's connection (it is session-based). I could restart the session in the library, but this means quite a bit of data transfer to fetch the contacts list and some users use 3g.
I can't edit the library's source, nor can I see it, so I don't know if it creates the sockets the right way.
What do I have to do to handle both situations correctly? I don't even understand why there is a difference.

You cannot re-extend background tasks like this; your app is likely to be terminated. If this is working, it's because you have the background voip mode enabled, not because you are restarting the background task.
Once you have set the voip plist entry, iOS will attempt to keep your app alive as long as possible and restart it if it does get terminated. From Implementing a VoIP App:
Including the voip value in the UIBackgroundModes key lets the system
know that it should allow the app to run in the background as needed
to manage its network sockets. An app with this key is also relaunched
in the background immediately after system boot to ensure that the
VoIP services are always available.
In addition to setting this key, if you need to periodically run code to keep your voip connection alive, you can use the setKeepAliveTimeout:handler: method on UIApplication.
See also Tips for Developing a VoIP App:
There are several requirements for implementing a VoIP app:
Add the UIBackgroundModes key to your app’s Info.plist file. Set the value of this key to an array that includes the voip string.
Configure one of the app’s sockets for VoIP usage.
Before moving to the background, call the setKeepAliveTimeout:handler: method to install a handler to be
executed periodically. Your app can use this handler to maintain its
service connection.
Configure your audio session to handle transitions to and from active use.
To ensure a better user experience on iPhone, use the Core Telephony framework to adjust your behavior in relation to cell-based
phone calls; see Core Telephony Framework Reference.
To ensure good performance for your VoIP app, use the System Configuration framework to detect network changes and allow your app
to sleep as much as possible.
Almost all of the documentation you need is on the Apple developer site.

Related

UIApplication. Background execution for a fixed amount of time

So, i want my app to do background execution for only a fixed amount of time, this is in case the user does not manually stop the app, and the app therefore in theory could run in background forever(is that even possible?).
I'm using the code below (just a test app) to test how long exactly a background task can run before ending. I read somewhere that 10 minutes is the longest we can do background execution, and there is no way to get beyond that(?). However, my code will only execute in the background for 3 minutes.
So to sum up my questions:
Is it possible to tell the app to execute in the background for x > 10 minutes?
2.Do i have any other options for something similar? (the actual app i need this implemented in, receives location updates in the background, the user could have the phone in the background for as long as 30 minutes, and suddenly not receiving updates would be bad)
- (void)viewDidLoad {
[super viewDidLoad];
counterTask = [[UIApplication sharedApplication]
beginBackgroundTaskWithExpirationHandler:^{
// do something }];
count=0;
theTimer=[NSTimer scheduledTimerWithTimeInterval:0.1
target:self
selector:#selector(countUp)
userInfo:nil
repeats:YES];
}
- (void)countUp {
if (count==10000) {
[theTimer invalidate];
[[UIApplication sharedApplication] endBackgroundTask:counterTask];
} else {
NSLog(#"asd");
count++;
NSString *currentCount;
currentCount=[[NSString alloc] initWithFormat:#"%d",count];
_theCount.text=currentCount;
long seconds = lroundf([[UIApplication sharedApplication] backgroundTimeRemaining]);
NSLog([NSString stringWithFormat:#"%ld",seconds]);
}
}
I read somewhere that 10 minutes is the longest we can do background execution, and there is no way to get beyond that(?). However, my code will only execute in the background for 3 minutes.
yes you are right before iOS 7 iOS allowed 10 minutes max for apps to execute in background , however since iOS 7 they have reduced this time to 180 seconds.
But if you want to get Location Updates in background than you can add Required Background modes property in your info.Plist file. Using this you will be able to run your app in background for getting location updates Apple will review your request while reviewing your app for app store submission so be sure to use this mode only if you using it for its actual purpose.
Following are various modes for which apple allows background execution you can take a look at it at Apples Doc on background execution
Edit
If you wish to stop getting location Updates after specific time once user goes to backGround you can do this
- (void)applicationDidEnterBackground:(UIApplication *)application {
[self performSelector:#selector(stopGettingLocationUPdates) withObject:nil afterDelay:1800];
}
-(void)stopGettingLocationUPdates{
[self.locationManager stopUpdatingLocation]
}
This will stop updates after 30 mins.
Your code is not running in the background. It is not testing what you want to test.
Apple's docs say:
Executing a Finite-Length Task in the Background Apps that are
transitioning to the background can request an extra amount of time to
finish any important last-minute tasks. To request background
execution time, call the
beginBackgroundTaskWithName:expirationHandler: method of the
UIApplication class.
The actual time you get is not specified and is probably decided ad hoc based on power consumption, memory needs and so on. They may be a maximum.
They go on to say:
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 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
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.

Maintain a Multipeer Connectivity session in Background via BackgroundTask?

I am trying to maintain a MultipeerConnectivity "session" when the application enters temporarily in the background, so I thought about using a background task as I've seen few times here ... The problem is I have no idea how to "maintain" the session with the UIBackgroundTask, can someone please post a hint
I don't care about the advertisers/browsers, it's okay to stop them, but I'd like the session to not disconnect as reconnecting is super buggy for the moment.
As per apple documentation "If the app moves into the background, the framework stops advertising and browsing and disconnects any open sessions. Upon returning to the foreground, the framework automatically resumes advertising and browsing, but the developer must reestablish any closed sessions" Refer: Apple doc
One way of extending the connection is as follows
Answering my own question, hoping it would help people in the same situation.
For people new to iOS development, "using a background service" simple means turning on the "Background Modes" option in the "Capabilities" tab of your target.
That alone should give your app around 10 minutes life in the background before it gets killed.
But, when the app goes to background, I use the "backgroundTimeRemaining" to know how much time I have left, it just starts at 180 (in sec, so 3 minutes), yet, the printing loop did continue to work passed three minutes, which means there is a need to manually code what should happen when the time is reached.
For Multipeer Connectivity, this is enough to maintain the connection alive when the app enters background, and it will still receive all messages/streams without a problem.
For the sake of stability, I do some cleaning as follow:
In the appDelegate.h
#property (nonatomic) UIBackgroundTaskIdentifier backgroundTask; //declaring a background task
In the appDelegate.m
- (void)applicationDidEnterBackground:(UIApplication *)application
{
self.backgroundTask = [application beginBackgroundTaskWithExpirationHandler:^
{
//This is called 3 seconds before the time expires
//Here: Kill the session, advertisers, nil its delegates,
// which should correctly send a disconnect signal to other peers
// it's important if we want to be able to reconnect later,
// as the MC framework is still buggy
[application endBackgroundTask:self.backgroundTask];
self.backgroundTask = UIBackgroundTaskInvalid; //Invalidate the background task
}];
}
- (void)applicationDidBecomeActive:(UIApplication *)application
{
// Here: We should init back the session, start the advertising and set the delegates from scratch
// This should allow the app to reconnect to the same session with more often than not
self.backgroundTask = UIBackgroundTaskInvalid; //Here we invalidate the background task if the timer didn't end already
}
I've asked this same question once on the apple developer forums. One of the Apple employees told me that basically all of the Multipeer connectivity should be considered off-limits when your app is not int the foreground.

Execute function every X minutes in background doesn't work

I use this code to execute function every X minutes:
- (void)executeEveryOneMinute
{
[self myFunction];
dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(60 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
[self executeEveryOneMinute];
});
}
And it works when app is in foreground.
But when app goes background it doesn't work anymore.
When I return app to foreground again it execute function once.
And continue to call function every minute again.
So how to make this to work in background too?
See the Background Execution and Multitasking section of the iOS App Programming Guide: App States and Multitasking for a discussion of the possibilities. You can, for example, keep the app running in the background for a few minutes in order to complete some finite length task. Or you can continue to run the app in the background for a longer period of time if it's performing one of a very particular list of functions (quoting from the aforementioned document):
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
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.
But, a fundamental design principle in iOS battery/power management is that random apps can not (and should not) continue to run in the background. If you share what precisely you're trying to do (namely, what precisely you're doing inside that executeEveryOneMinute method), though, we can offer counsel on how to achieve the desired effect, if possible.
If you're trying to have an upload continue in the background, in iOS 7 and greater, you should consider using NSURLSession with a background session configuration ([NSURLSessionConfiguration backgroundSessionConfiguration:identifier]; there is a similar method in iOS 8). This will continue to attempt to upload (automatically, without further intervention on your part) not only after your app has left the foreground, but even after the app is terminated (e.g. due to memory pressure or a crash). AFNetworking offers a NSURLSession-based class, AFURLSessionManager, which supports this (though it's not NSOperation-based). This way, you enjoy background uploads, but conforms to Apple guidelines on background operation, notably with less dramatic battery impact than retrying yourself every 60 seconds.
I'd suggest you refer to the latter part of WWDC 2013 video What’s New in Foundation Networking, which demonstrates this process (they're doing a download, but the idea is the same for uploads).
Timer works on Main thread. When application goes into background, its timers become invalid. So, you cant do the same when application goes into background.
You can't do this with help of timer as it will be invalidated in background. You can try check this.
You should use background tasks to achieve what you want
UIApplication* app = [UIApplication sharedApplication];
task = [app beginBackgroundTaskWithExpirationHandler:^{
[app endBackgroundTask:task];
task = UIBackgroundTaskInvalid;
}];
// Start the long-running task and return immediately.
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
// Do the work associated with the task.
NSLog(#"Started background task timeremaining = %f", [app backgroundTimeRemaining]);
if (connectedToNetwork) {
// do work son...
}
[app endBackgroundTask:task];
task = UIBackgroundTaskInvalid;
});

Repeating a task when app is in background (e.g. pull something from a server), without APNs

Is there a good, Apple-approved alternative to using push notifications to trigger an app to run some code (in particular: pull new messages from a server) in a regular interval?
Disguising as VoIP app is not a good option (won't be approved, see iPhone: repeating background task)
I cannot use location updates, it should work if the user does not move around
In the simulator, using beginBackgroundTaskWithExpirationHandler with dispatch_async gives you 10 minutes of background time, and I found out that if the background "restarts itself", the backgroundTimeRemaining property always seems to be reset to 10 minutes. Here's the code.
- (void) work
{
UIApplication *application = [UIApplication sharedApplication];
NSLog(#"bg %# (T-%.1f seconds)",
[NSDate date],
[application backgroundTimeRemaining]);
sleep(10);
[application endBackgroundTask:_bgTask];
_bgTask = UIBackgroundTaskInvalid;
[self startTask];
}
- (void)startTask
{
UIApplication *application = [UIApplication sharedApplication];
_bgTask = [application beginBackgroundTaskWithExpirationHandler:^{
NSLog(#"expired at %#", [NSDate date]);
[application endBackgroundTask:_bgTask];
_bgTask = UIBackgroundTaskInvalid;
}];
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_BACKGROUND,
0),
^{ [self work]; });
}
- (BOOL) application:(UIApplication*)application didFinishLaunchingWithOptions:(NSDictionary*)launchOptions
{
/* ... */
[self startTask];
/* ... */
}
Would that be an accepted practice to run something in the background? I mean, most of the time I would just sleep(...) until I want to repeat a network request or do something useful, but the app would never really enter full background mode. Does anyone have experience with this approach? Hint: Only tested on simulator without other running apps.
The Apple-approved alternatives are listed in https://developer.apple.com/library/ios/documentation/iPhone/Conceptual/iPhoneOSProgrammingGuide/BackgroundExecution/BackgroundExecution.html
Looking at "Table 3-1 Background modes for apps", the two relevant alternatives for repeatedly getting info from a server are "Background fetch" or "remote-notification".
"remote-notification" is push notifications, which you say you don't want to use.
Therefore, "Background fetch" is the relevant choice. For example, see https://blog.newrelic.com/2016/01/13/ios9-background-execution "Downloading remote content opportunistically".
However, this does not give you (the developer) the degree of control you would have in Android. There is "setMinimumBackgroundFetchInterval", but notice that this is a MINIMUM: iOS decides when to call into your app for the next background fetch. (Apple is focused on overall battery usage and device responsiveness; once your app is in the background, design to work gracefully with however little attention it is given.)
NOTE: If the user kills your app, "Background fetch" will be killed with it. This is by design. (And is a good thing, from the user's viewpoint: most apps should stay dead if killed.)
Consider using a combination of "push notification" (remote-notification) and "Background fetch". For example, if a user permits "push notifications" by your app, then do one push daily, with a text notification to user. If they open that notification, that will open your app. Then begin the data fetching. If they hit Home button, use "Background fetch" to continue data fetching periodically through the day.
Users who are very battery-conscious may kill all their apps periodically. If they don't want to be bothered by your app today, they will ignore or delete your app's push notification. Consider this a good thing: you won't annoy users by draining battery on days that they aren't actively using your app.
Users who like to have tight control over what is running on their phone WILL NOT permit push notifications for your app. (For instance, I hate to receive daily text notifications. Don't call me, I'll call you.) In this case, once your app is killed, there is nothing that you can do (since push notification is the only way to resurrect your dead app, and I, the user, have said "No" to that). Be sure to consider how you will serve such users. (Your content may be stale when they first re-open your app.)
You can't do this on a normal iphone. And if you found out a way to do it, Apple would eventually fix the loophole and reject your app.
I don't know about jailbroken iphones, I suspect it might be possible on them somehow.
I think you can use "local notifications" to trigger something to occur at a specific time.
https://developer.apple.com/library/content/documentation/NetworkingInternet/Conceptual/RemoteNotificationsPG/SchedulingandHandlingLocalNotifications.html#//apple_ref/doc/uid/TP40008194-CH5-SW1

Run app for more than 10 minutes in background

I am trying to keep the iOS app in active state for more than 10 mins when it enters in background state.
How can I implement this.
See "Background Execution" section of the iPhoneAppProgrammingGuide. In short, your app must be one of these types:
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
And you must add to the Info.plist as follows:
Add the UIBackgroundModes key to your
Info.plist file and set its value to an array containing one or more of the following strings:
audio—The app plays audible content to the user while in the background. (This content includes streaming audio or video content using AirPlay.)
location—The app keeps users informed of their location, even while it is running in the background.
voip—The app provides the ability for the user to make phone calls using an Internet connection.
newsstand-content—The app is aNewsstand app that downloads and processesmagazine or newspaper
content in the background.
external-accessory—The app works with a hardware accessory that needs to deliver updates on a
regular schedule through the External Accessory framework.
bluetooth-central—The app works with a Bluetooth accessory that needs to deliver updates on a
regular schedule through the CoreBluetooth framework
Note that part of the review process will be checking to make sure that your app does what it says it's doing with regard to background processing.
Here's what I've done using beginBackgroundTaskWithExpirationHandler.
Write a method that starts a background task.
Inside that background task, run a NSTimer with a scheduled (non repeating) time that is under 10 minutes. For the purposes of my situation I was using 5 minutes.
Once the NStimer's selector fires, end the background task and then instantly call the method that you wrote earlier to start off another background task.
If you want to schedule methods to run at specific times, you will have to check for them in the background task.
This solution isn't really ideal and is still power hungry but will do what you want.
Edit: Since iOS7, I suggest you read this excellent post. Note that this article was last updated in 2013 and is probably irrelevant now.
Only certain types of apps are allowed to run in the background. See the "Implementing Long-Running Background Tasks" section of this guide.
If you aren't requesting permissions to do background processing you can use UIApplication's beginBackgroundTaskWithExpirationHandler but you cannot get extra time.
This code makes your iOS app run indefinitely in the background. Copy and paste the below methods into a singleton / manager which handles the tasks you need to perform in the background.
// #interface
// Declare Private property
#property (nonatomic) UIBackgroundTaskIdentifier backgroundTask;
//#end
// ...
// Copy into
//#implementation
- (void)setupBackgrounding {
[[NSNotificationCenter defaultCenter] addObserver: self selector: #selector(appBackgrounding:)
name: UIApplicationDidEnterBackgroundNotification
object: nil];
[[NSNotificationCenter defaultCenter] addObserver: self selector: #selector(appForegrounding:)
name: UIApplicationWillEnterForegroundNotification
object: nil];
}
- (void)appBackgrounding: (NSNotification *)notification {
[self keepAlive];
}
- (void) keepAlive {
self.backgroundTask = [[UIApplication sharedApplication] beginBackgroundTaskWithExpirationHandler:^{
[[UIApplication sharedApplication] endBackgroundTask:self.backgroundTask];
self.backgroundTask = UIBackgroundTaskInvalid;
[self keepAlive];
}];
}
- (void)appForegrounding: (NSNotification *)notification {
if (self.backgroundTask != UIBackgroundTaskInvalid) {
[[UIApplication sharedApplication] endBackgroundTask:self.backgroundTask];
self.backgroundTask = UIBackgroundTaskInvalid;
}
}
You can't. Unless your app uses audio, voip or gps. What you can do is notify the user (via local notifications) that the time is almost up and ask him to open/close the app.
Also if you just need to notify the user, you can use push notifications.
https://github.com/yarodevuci/backgroundTask Check my code here I am using audio player that plays blank wav file Works perfectly on IOS 8 Battery usage around 10% in 24 hour period
How to use:
var backgroundTask = BackgroundTask()
backgroundTask.startBackgroundTask() //Starts playing blank audio file. You can run NSTimer() or whatever you need and it will continue executing in the background.
backgroundTask.stopBackgroundTask() //Stops the task
Warning: Apple will reject this if you try to submit it!
If your App type is not one of VOIP/Audio/Location....(check Background Modes),
or you don't want to specify your App as a background App, you can implement beginBackgroundTaskWithName:expirationHandler or beginBackgroundTaskWithExpirationHandler to ask for more time to run your process in background. You can find the detailed description here
Apps moving to the background are expected to put themselves into a quiescent state as quickly as possible so that they can be suspended by the system. If your app is in the middle of a task and needs a little extra time to complete that task, it can call the beginBackgroundTaskWithName:expirationHandler: or beginBackgroundTaskWithExpirationHandler: method of the UIApplication object to request some additional execution time. Calling either of these methods delays the suspension of your app temporarily, giving it a little extra time to finish its work. Upon completion of that work, your app must call the endBackgroundTask: method to let the system know that it is finished and can be suspended.
Each call to the beginBackgroundTaskWithName:expirationHandler: or beginBackgroundTaskWithExpirationHandler: method generates a unique token to associate with the corresponding task. When your app completes a task, it must call the endBackgroundTask: method with the corresponding token to let the system know that the task is complete. Failure to call the endBackgroundTask: method for a background task will result in the termination of your app. If you provided an expiration handler when starting the task, the system calls that handler and gives you one last chance to end the task and avoid termination.

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