I have used VoIP and remote notification as background modes.
I kept my application idle in background for overnight testing.
I have written following code in applicationDidEnterBackground
- (void)applicationDidEnterBackground:(UIApplication *)application
{
[[UIApplication sharedApplication] setKeepAliveTimeout:600 handler:^{
NSString *message = #"voip keep alive timeout executed....";
NSLog(#"%#",message);
[Logger addEntry:CAT_ML_CORE andSubCategory:SUBCAT_DEBUG andMessage:message];
}];
}
after 1 day keeping application idle in background I found "voip keep alive timeout executed...." got printed in my logs.
This indicated that my app is alive.
But when I send push notification to my app "didreceiveremotenotification fetchcompletionhandler" method doesn't get called.
Which is contradictory to the statement made by Apple "Unlike the application:didReceiveRemoteNotification: method, which is called only when your app is running, the system calls didreceiveremotenotification fetchcompletionhandler method regardless of the state of your app. If your app is suspended or not running, the system wakes up or launches your app and puts it into the background running state before calling the method."
Can someone please tell me why this is happening?
Make sure your APNS payload has "content-available"
content-available - number - Provide this key with a value of 1 to indicate that new content is available.This is used to support Newsstand apps and background content downloads.
https://developer.apple.com/library/ios/documentation/NetworkingInternet/Conceptual/RemoteNotificationsPG/Chapters/ApplePushService.html
There is a small bug in my App.
My App displays notifications at specific times when the App is running and cancel all of them whenever a button is switched.
My problem is that whenever a user closes the App using the multitasking feature of iOS the notifications are still showing up.
I tried to add the following code which doesn't work:
- (void)applicationWillTerminate:(UIApplication *)application
{
// Called when the application is about to terminate. Save data if appropriate. See also applicationDidEnterBackground:.
[[UIApplication sharedApplication] cancelAllLocalNotifications];
}
The problem is that my App should show notifications when the App is running but shouldn't show notifications when the App is terminated.
Why does the above code not work?
The correct answer is that this cannot currently be done by a multitasking app. One solution is to set a flag in our info.plist declaring your app wants to be killed when the user switches to another app - then you will get the willTerminate message (but get killed then).
There are huge numbers of threads on this topic, one which quotes an Apple doc that tells you backgrounded apps that are terminated do NOT get the willTerminate message is here.
For me, this just means I can now close an open bugreport out with a 'cannot fix' resolution :-)
Just because your app is visible in the app-changer, it doesn't mean it is still running.. it can get closed at any point. You cannot differentiate between the OS closing your app or the user closing your app.
Perhaps a button would be the solution? A button that cancels all notifications?
Or you run a real background task (which can last for about 5 minutes) and stop all notifications afterwards. Or you just schedule the notifications for the next 5-10 minutes and that's it.
For what are you using them?
We're currently developing an iOS app that needs to check location in the background. At first, we tried to use significant location changes, but they aren't accurate enough/don't trigger often enough. We considered using region monitoring, but from what I've read online, that isn't always accurate either, and you also have the problem of a limited number of regions to monitor. (We may eventually try region monitoring.) At the moment, however, we're attempting to use the standard location updates to track the user location in the background, with a plan to have it at check at intervals of 5 minutes, or so.
The app is registered for location updates in the background (using 'App registers for location updates' for 'Required background modes'), and we start a background task which checks the location once, stops location updates, then uses NSThread sleepForTimeInterval: to (at the moment, while we're in development) pause the task for 10 seconds. It then checks the location once again, stops location updates, pauses for 10 seconds, etc.
This appears to work as expected... When the app goes into the background, we receive a log/notification with our location update every 10 seconds, and when the app is reopened, the logs/notifications stop. However, the problem is that when the app then goes into the background for a second time, it appears the original background task was never cancelled, and a new one is created, so there are now two tasks running, each checking location at 10 sec on intervals. If the app is opened/sent to the background multiple times, then a background task is started for each of them.
I thought about setting a flag to say "has the app been sent to the background at least once?", and only run the task if it's the first time it's sent to the background, but this seems to cause additional problems, and (as a relatively new iOS developer) I'm curious as to why the background tasks aren't being cancelled when the app enters the foreground.
The AppDelegate.h file contains...
#interface AppDelegate : UIResponder <UIApplicationDelegate, CLLocationManagerDelegate> {
UIWindow *window;
UINavigationController *navigationController;
UIBackgroundTaskIdentifier bgTask;
BOOL inBackground;
}
The AppDelegate.m file contains...
- (void)applicationDidEnterBackground:(UIApplication *)application {
inBackground = YES;
bgTask = [[UIApplication sharedApplication] beginBackgroundTaskWithExpirationHandler:^{
[[UIApplication sharedApplication] endBackgroundTask:bgTask];
bgTask = UIBackgroundTaskInvalid;
}];
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
while (inBackground == YES) {
NSLog(#"%#", #"Check location...");
[locationManager startUpdatingLocation];
[NSThread sleepForTimeInterval:10];
}
[[UIApplication sharedApplication] endBackgroundTask:bgTask];
bgTask = UIBackgroundTaskInvalid;
});
}
- (void)applicationWillEnterForeground:(UIApplication *)application
{
// Called as part of the transition from the background to the active state; here you can undo many of the changes made on entering the background.
inBackground = NO;
[[UIApplication sharedApplication] endBackgroundTask:bgTask];
bgTask = UIBackgroundTaskInvalid;
}
The location updates are working as expected, I just can't work out why the background tasks aren't being cancelled/ended when the app enters the foreground. I do wonder if it's anything to do with the NSThread sleepForTimeInterval:, but I'm not sure if it is, or how to fix it (if indeed, it is). Thanks, in advance, for any help!
You don't manage location updates by sleeping and then requesting them. You manage location updates by setting "location" in UIBackgroundMode (as you do), and then implementing a CLLocationManagerDelegate. This has nothing to do with beginBackgroundTaskWithExpirationHandler:. That's for requesting additional time (up to about 10 minutes) to finish a given operation. You shouldn't be calling that at all just to get location updates.
Once you've registered as a location app in UIBackgroundMode, you will automatically get updates whenever the location changes within the accuracy you specified for your location manager. The system will do all the work for you.
What you're describing may actually hurt battery life because it frustrates the OS's ability to manage the multiple location sensors (of which the GPS is just one). Tell the OS what you need by setting the correct accuracy (if significant changes is too coarse), and let it do its job. Getting really accurate location from the GPS is expensive. You should do battery testing before assuming that it's cheaper to do every 5 minutes than to leave on. The best thing you can do to preserve power is to reduce the required accuracy. You might turn it down to a coarse level, and then when you come to the foreground move it to an accurate level. But keeping track of precisely where the user is every 5 minutes is going to be expensive. It's hard to fix that.
BTW, what you're really trying to do here is get to run "something" every 5 minutes. There is no mechanism for that in iOS. You can either ask for location services or not (and configure it in various ways). You can't ask for "I want to wake up every five minutes and ... do anything." After about 10 minutes you're going to be killed if you don't call endBackgroundTask:.
To your question of why the tasks aren't being cancelled, see How to use beginBackgroundTaskWithExpirationHandler for already running task in iOS. As I said, this "background tasks" is not the tool you want for this problem. It's completely unrelated.
I'm fairly certain that your instance variable bgTask is being reallocated when the app comes back into the foreground, so the value doesn't contain the identifier you're looking to kill. Consider saving this identifier in NSUserDefaults or something a little more permanent and retrieving it later.
I've got an app that changes the screen brightness with [UIScreen mainScreen].brightness = newBrightness, and I want to restore the brightness to it's previous state when the user finishes using it.
I've tried these two delegate methods:
- (void)applicationDidEnterBackground:(UIApplication *)application
- (void)applicationWillResignActive:(UIApplication *)application
But without much success. I suspect my app must be in the foreground to change the brightness? When I change the brightness in didEnterBackgroundMethod, it has no effect at all. When I use willResignActive it does restore the brightness if I switch to another app, but it has no effect when I press the home button.
Are there any notifications or delegate methods that are executed before the app leaves the foreground?
It seems this happens to others as well: see this S.O. post.
Only way around it seems to be forgetting about setBrightness and simulating it by overlaying a black-semi-transparent on your view...
OLD ANSWER:
willResignActive should also be called when you press the home button before the application enters the background state.
This method is called to let your application know that it is about to move from the active to inactive state. This can occur for certain types of temporary interruptions (such as an incoming phone call or SMS message) or when the user quits the application and it begins the transition to the background state. An application in the inactive state continues to run but does not dispatch incoming events to responders.
This is also the behavior I witness. So, my guess (but it's just a guess) is that your app is not set to support background, so that when pressing the home button it is terminated. In this case applicationDidEnterBackground is not called.
I would suggest to check the info.plist file in your project for the UIApplicationExitsOnSuspend or "Select Application does not run in background" key.
Furthermore, you could try and put some breakpoints (or NSLog traces) in those functions and check whether they are effectively called as expected.
According to Apple´s DevForum it seems to be a bug that Apple don´t want to fix soon.
I'm writing following code that opens browser when app will be going to background:
- (void)applicationWillResignActive:(UIApplication *)application
{
/*
Sent when the application is about to move from active to inactive state. This can occur for certain types of temporary interruptions (such as an incoming phone call or SMS message) or when the user quits the application and it begins the transition to the background state.
Use this method to pause ongoing tasks, disable timers, and throttle down OpenGL ES frame rates. Games should use this method to pause the game.
*/
[[UIApplication sharedApplication] openURL:[NSURL URLWithString:#"http://www.google.com"]];
}
but its not opening. Any suggestions?
Can I open browser in "applicationWillResignActive" or not?
You code looks fine so I guess that iOS won't let you do it. Your app has been told to go into the background - you don't get to open new apps!
PS :
Why would you ever want to do this - surely this will just really really annoy the user?