Question

I am trying to use XMPPFramework to show background notifications in the “10 minute window” before the application is terminated. It appears that all of the network requests are being queued while it is in the background, and xmppStream:didReceiveMessage: isn’t being called until the app is brought back to the foreground.

I have noticed apps like Verbs support this behavior. They are clearly not a VoIP app, so I am curious as to how they accomplished this behavior.

Answer 1

In case anyone else has this issue, you can solve it by adding this code to your App Delegate. My full source code is here if you want to check it out: OTRAppDelegate.m. The other relevant code is in receiveMessage: of OTRBuddy.m.

- (void)applicationDidEnterBackground:(UIApplication *)application
{
    NSLog(@"Application entered background state.");
    NSAssert(self.backgroundTask == UIBackgroundTaskInvalid, nil);
    self.didShowDisconnectionWarning = NO;

    self.backgroundTask = [application beginBackgroundTaskWithExpirationHandler: ^{
        dispatch_async(dispatch_get_main_queue(), ^{
            NSLog(@"Background task expired");
            if (self.backgroundTimer) 
            {
                [self.backgroundTimer invalidate];
                self.backgroundTimer = nil;
            }
            [application endBackgroundTask:self.backgroundTask];
            self.backgroundTask = UIBackgroundTaskInvalid;
        });
    }];

    dispatch_async(dispatch_get_main_queue(), ^{
        self.backgroundTimer = [NSTimer scheduledTimerWithTimeInterval:10 target:self selector:@selector(timerUpdate:) userInfo:nil repeats:YES];
    });
}

- (void) timerUpdate:(NSTimer*)timer {
    UIApplication *application = [UIApplication sharedApplication];

    NSLog(@"Timer update, background time left: %f", application.backgroundTimeRemaining);

    if ([application backgroundTimeRemaining] < 60 && !self.didShowDisconnectionWarning) 
    {
        UILocalNotification *localNotif = [[UILocalNotification alloc] init];
        if (localNotif) {
            localNotif.alertBody = EXPIRATION_STRING;
            localNotif.alertAction = OK_STRING;
            [application presentLocalNotificationNow:localNotif];
        }
        self.didShowDisconnectionWarning = YES;
    }
    if ([application backgroundTimeRemaining] < 10) 
    {
        // Clean up here
        [self.backgroundTimer invalidate];
        self.backgroundTimer = nil;
        [application endBackgroundTask:self.backgroundTask];
        self.backgroundTask = UIBackgroundTaskInvalid;
    }
}

- (void)applicationWillEnterForeground:(UIApplication *)application
{

}

- (void)applicationDidBecomeActive:(UIApplication *)application
{
    /*
     Restart any tasks that were paused (or not yet started) while the application was inactive. If the application was previously in the background, optionally refresh the user interface.
     */
    NSLog(@"Application became active");
    if (self.backgroundTimer) 
    {
        [self.backgroundTimer invalidate];
        self.backgroundTimer = nil;
    }
    if (self.backgroundTask != UIBackgroundTaskInvalid) 
    {
        [application endBackgroundTask:self.backgroundTask];
        self.backgroundTask = UIBackgroundTaskInvalid;
    }

    application.applicationIconBadgeNumber = 0;
}