Run NSTimer from a background task

Question

I'd like to use a NSTimer as a background task. I've written this code:

UIBackgroundTaskIdentifier bgTask;
        UIApplication  *app = [UIApplication sharedApplication];
        bgTask = [app beginBackgroundTaskWithExpirationHandler:^{
            [app endBackgroundTask:bgTask];
        }];
        self.silenceTimer = [NSTimer scheduledTimerWithTimeInterval:30 target:self selector:@selector(findlocation:) userInfo:nil repeats:NO];

But it doesn't fire the findlocation method after 30 seconds. Please guide me how to do this.

possible duplicate of [How do I make my App run an NSTimer in the background?](http://stackoverflow.com/questions/9220494/how-do-i-make-my-app-run-an-nstimer-in-the-background) — Jano, Jan 23 '13 at 12:09
Try this http://stackoverflow.com/questions/4656214/iphone-backgrounding-to-poll-for-events — yen, Jan 24 '13 at 12:39

score 0 · Answer 1 · edited May 23 '17 at 12:18

0

NSTimer are paused when the app is in background state.

You'll have to start some background task to do what you want. But even with that, you will be limited to a certain amount of time after the app was put in background.

Real backgrounding behavior is only granted for location tracking, VoIP or Audio apps. Other apps must face limitations: once in background, you are given an amount of time to complete tasks you start with beginBackgroundTaskWithExpirationHandler: (backgroundTimeRemaining).

Check this for more information http://developer.apple.com/library/ios/#documentation/iphone/conceptual/iphoneosprogrammingguide/BackgroundExecution/BackgroundExecution.html

For a clean solution, check the accepted answer of this question How do I make my App run an NSTimer in the background?

edited May 23 '17 at 12:18

Community

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1

answered Jan 23 '13 at 12:02

DD_

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before using the timer on that thread, i am using the CLLocationmanager – Kevin Char Jan 23 '13 at 12:05
@KevinChar check the answer in the link, similar situation like yours. right? – DD_ Jan 23 '13 at 12:06
Iam already called the startlocationupdatingmethod before start the timer. – Kevin Char Jan 23 '13 at 12:18

score 0 · Answer 2 · edited May 23 '17 at 10:24

This code to play the sound when application enter into background you can customize it for your own use

- (void)applicationDidEnterBackground:(UIApplication *)application{
    backgroundTask = [application beginBackgroundTaskWithExpirationHandler: ^{
        dispatch_async(dispatch_get_main_queue(), ^{
            if (backgroundTask != UIBackgroundTaskInvalid)
            {
                [application endBackgroundTask:backgroundTask];
                backgroundTask = UIBackgroundTaskInvalid;
            }
        });
    }];
    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{

        [NSThread sleepForTimeInterval:3];
        [self startPlayingInBackground:@"default.aif"];
        NSLog(@"Time remaining: %f",[application backgroundTimeRemaining]);

        dispatch_async(dispatch_get_main_queue(), ^{
            if (backgroundTask != UIBackgroundTaskInvalid)
            {
                // if you don't call endBackgroundTask, the OS will exit your app.
                [application endBackgroundTask:backgroundTask];
                backgroundTask = UIBackgroundTaskInvalid;
            }
        });
    });
}

The line below is the code with help of which m playing the sound it's my objective c function all

[self startPlayingInBackground:@"default.aif"];

reference from

score 0 · Answer 3 · answered Aug 01 '13 at 06:07

UIBackgroundTaskIdentifier bgTask;
    UIApplication  *app = [UIApplication sharedApplication];
    bgTask = [app beginBackgroundTaskWithExpirationHandler:^{
        [app endBackgroundTask:bgTask];
    }];
    self.silenceTimer = [NSTimer scheduledTimerWithTimeInterval:30 target:self selector:@selector(findlocation:) userInfo:nil repeats:NO];

[[NSRunloop mainRunLoop] addTimer:self.silenceTimer forMode:NSDEfaultRunLoopMode];

score -1 · Accepted Answer · answered Jan 23 '13 at 12:02

-1

Try this code:

dispatch_queue_t backgroundQueue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
 dispatch_source_t timerSource = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0, 0, backgroundQueue);
 dispatch_source_set_timer(timerSource, dispatch_time(DISPATCH_TIME_NOW, 0), 10.0*NSEC_PER_SEC, 0*NSEC_PER_SEC);
 dispatch_source_set_event_handler(timerSource, ^{
     if(queue)
         [self findlocation];
 });
 dispatch_resume(timerSource);

answered Jan 23 '13 at 12:02

Rox

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where can i mention 30 seconds and what is queue – Kevin Char Jan 23 '13 at 12:03
here queue is a bool. Set its value to true – Rox Jan 23 '13 at 12:12
If i writw like this then that method will be called for every 30 seconds.I don't want like that,i need to call for first time only. – Kevin Char Jan 23 '13 at 12:16
set queue=FALSE in findlocation – Rox Jan 23 '13 at 12:17
Everytime it will be called that method suddenly after run this code.NOt waiting that 30 seconds – Kevin Char Jan 23 '13 at 12:24
if you want to run only one time then why not you directly use NSTimer? – Rox Jan 23 '13 at 12:56
[self findlocation]; is never fired – Jacek Kwiecień Dec 13 '13 at 16:00

Run NSTimer from a background task

4 Answers4