dispatch_after is limited to 10 seconds?

Question

I\'m developing an app which is running in background. Sometimes I need to tell the user that something is happenning so I play a sound a certain number of times. To do that I m

Answer 1

I suspect that chaining asynch blocks to play sounds at regular intervals is a bit of an overkill. Perhaps something simpler along the following lines would be easier to understand and maintain:

// To initiate the alarm:
[self fiBGTemps: ALARM];

- (void)fiBGTemps:(int)sender
{
    switch (sender) {
       ...
       case ALARM:
           dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^(void) {
                int count = 0;
                while (count < NUM_ALARM /* AND not interrupted by user? */) {
                    sleep(2);
                    AudioServicesPlaySystemSound(alarma);
                    AudioServicesPlaySystemSound(kSystemSoundID_Vibrate);
                    count++;
                }
            });
            break;
        ...
    }
}

Answer 2

Problem solved.

This is what happens. When an app is running in background and and it is executed a task, this task is running in background as well but the system allows only a certain amount of time (10s apron.) in order to safe battery. So it is only for a specific tasks (localization, download, etc.).

I my case I need a little more time so the solution is to define the task as a UIBackgroundTask in such a way that will be the task who notify the system when it is completed and thus can be terminated.

this is the code where it is called the task:

    UIApplication *application = [UIApplication sharedApplication];
    __block UIBackgroundTaskIdentifier background_task;
    background_task = [application beginBackgroundTaskWithExpirationHandler: ^{
        [application endBackgroundTask: background_task];
        background_task = UIBackgroundTaskInvalid;
    }];

    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
        [self fiBGTemps:@(ALARM)];
        [application endBackgroundTask: background_task];
        background_task = UIBackgroundTaskInvalid;
    });

And here you can see the discussion on the Apple Forums where they explain this better than me.

AppleForums discussion

I hope this helps.

Kanick

Answer 3

You can try with re-setting the delay value after it exceed 10s of the total delayed time or may be after it has played sound for certain amount of time.