There's a way to notify a object when the method "applicationDidEnterBackground" of application delegate is called but just getting the applicationObject.
I need to do some action when application get on background but I just have access to the application object through "[UIApplication sharedApplication]".
Note: I need those 3 methods applicationWillTerminate, applicationWillEnterForeground, applicationDidEnterBackground but I can't access to applicationDelegate methods.
You can use NSNotificationCenter to inform your class that these methods are being called.
In the init register the the correct notification:
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(applicationWillTerminateNotification:) name:UIApplicationWillTerminateNotification object:nil];
This will call a method this method, which you will have to add in you class:
- (void)applicationWillTerminateNotification::(NSNotification *)notifictaion{
}
The notification that you want to add are: UIApplicationWillTerminateNotification, UIApplicationWillEnterForegroundNotification and UIApplicationDidEnterBackgroundNotification
Don't forget to unregistered the you class instance in the dealloc of you class, even in ARC:
-(void) dealloc {
[[NSNotificationCenter defaultCenter] removeObserver:self name:UIApplicationWillTerminateNotification object:nil];
}
I had the similar problem. My solution was to get the instance of AppDelegate and register my object as observer:
AppDelegate* appDelegate = (AppDelegate*)[[UIApplication sharedApplication] delegate];
[appDelegate addApplicationDidEnterBackgroundObserver:myobject];
// and later...
[appDelegate removeObserver:myobject];
sure the solution by rckoenes is more elegant.
Related
I have two class which uses NSNotification to communicate with each other.
Currently, i have an issue with notification being fired twice, i've double/triple/even more checked that observer is not added more then 1 time, notification not being posted twice, did global search on my project for same notification.
My code is like below
Added Notification Observer
[[NSNotificationCenter defaultCenter] removeObserver:self name:notification_deleteMediaFromGallery object:nil];
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(notificationReceiver:) name:notification_deleteMediaFromGallery object:nil];
Notification Receiver
- (void)notificationReceiver:(NSNotification*)notification {
if ([notification.name isEqualToString:notification_deleteMediaFromGallery]) {
if ([[notification.userInfo objectForKey:#"kind"] integerValue]==GalleryKindPhoto) {
//My statements
}
else if ([[notification.userInfo objectForKey:#"kind"] integerValue]==GalleryKindVideo) {
//My statements
}
}
}
Post Notification
dispatch_async(dispatch_get_main_queue(), ^{
[_browser reloadData];
[[NSNotificationCenter defaultCenter] postNotificationName:notification_deleteMediaFromGallery object:nil userInfo:#{#"index":#(_browser.currentIndex), #"kind":#(self.kind), #"function":[NSString stringWithFormat:#"%s",__PRETTY_FUNCTION__]}];
});
I have also tried this solution by EmptyStack but not get it to work.
I'll be very thankful to you if you could help me solve this issue.
Thanks.
Edit
NOTE
I've added observer in my viewdidload, and cant add/remove observer from viewwillappera/viewwillappear or viewdidappear/viewdiddisappear because the next viewcontroller which will be pushed on current viewcontroller will post notifications
I think you need to write dealloc method in your view controller. And remove All Notification observer in dealloc method,
- (void)dealloc
{
// Deregister observer
[[NSNotificationCenter defaultCenter] removeObserver:self name:notification_deleteMediaFromGallery object:nil];
}
Hi please make sure your method is not calling two time from where you are firing notification.
& please add your notification observer in viewWillDisappear method.
In my application has a view controller named "Home" with a textField.
I read about applicationDidEnterBackground and applicationWillTerminate methods in the AppDelegate file.
I know how to create, save, read data from a file.
My question is, How I can get an NSString from the "Home" viewController (that there store the textField data) to the AppDelegate applicationDidEnterBackground method and do there all my things with that data?
You could use NSNotificationCenter to register for a notification in your view controller that fires off whenever you enter applicationDidEnterBackground or applicationWillTerminate.
So in either of those methods you put something like
[[NSNotificationCenter defaultCenter] postNotificationName:#"someDescriptiveName" object:self userInfo:#{#"key" : #"value"}];
userInfo expects an NSDicitonary and you can pass it any type of object in there, in your case you dont need to pass anything from here back to your viewcontroller, your just using it as a means to let your view controller know the app is closing.
In your view controller you would register for that notification with something like this
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(methodToCall:) name:#"someDescriptiveName" object:nil];
Then whenever your appDelegate post that notification, your view controller which is registered to listen for it would fire off "methodToCall" which can be a method you right to do anything and it takes in an nsnotification which then lets you access the nsdicitonary its carrying.
- (void)methodToCall:(NSNotification *)notif{
NSLog(#"methodToCall fired with data %#",[[notif userInfo]valueForKey:#"key"]);}
You can do this with the help of this inside your controller:
-(id)init
{
if((self = [super init]))
{
[[NSNotificationCenter defaultCenter] addObserver:self
selector:#selector(appDidEnterBackground:)
name:UIApplicationDidEnterBackgroundNotification
object:[UIApplication sharedApplication]];
}
return self;
}
-(void)appDidEnterBackground:(NSNotification *)note {
NSLog(#"appDidEnterBackground");
}
you can also use applicationWillTerminate in place of UIApplicationDidEnterBackgroundNotification
Notification only called the function when observer_ViewController is active
AppDelegate.m
[[NSNotificationCenter defaultCenter] postNotificationName:kNewShipNotifaction object:ship];
observer_ViewController.m
-(void)viewDidLoad{
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(newShipCome:) name:kNewShipNotifaction object:nil];
}
- (void)newShipCome:(NSNotification *)notifacation{
[self updateNotifyWithShip:notifacation.object];
}
Notification didn't call the newShipCome:(NSNotification *)notification method when I'm in another viewController. When I switched to the observer_ViewController, the method still didn't get called.
So...how can I get notification update correctly when I'm not in the observer_ViewController ?
remove de-register code form viewWillDisappear it will work
Hi i am trying to use NSNotification center in my application.The selector method is not being called from the code.I found similar questions in this site like this, but still i am unable to resolve the error.
i am posting notification in appdelegate did finish launching as:
[[NSNotificationCenter defaultCenter] postNotificationName:#"ualert" object:self userInfo:userDict];
adding an observer in one of the view controller as:
[[NSNotificationCenter defaultCenter] addObserver:self
selector:#selector(remoteNotificationReceived:)
name:#"ualert"
object:nil];
my selector method is:
- (void)remoteNotificationReceived:(NSNotification *)notification
{
NSLog(#"Notification: %#", notification.userInfo);
}
removing observer as:
- (void)dealloc
{
[[NSNotificationCenter defaultCenter] removeObserver:self];
}
You are posting ualert in applicationDidFinishLaunching which will necessarily occur before your view controller is loaded (and therefore before you have added the observer for the notification).
I have a class called game.h and it has an instance method called pause. How can I call this from app delegate when my game goes into the background?
I know that you use - (void)applicationWillResignActive:(UIApplication *)application, but I want to call pause on my existing instance.
Using NSNotificationCenter.
In your instance of the game class, add self as an observer to the UIApplicationWillResignActiveNotification notification.
In your game class, somewhere, you need the following snippet:
[[NSNotificationCenter defaultCenter]
addObserver:self
selector:#selector(pause)
name:UIApplicationWillResignActiveNotification
object:nil];
This should probably go in init.
This notification is fired by applicationWillResignActive. The addObserver:selector:name:object: method sets your object up to call the selector you tell it whenever it receives that notification.'
Don't forget to remove self as an observer in dealloc.
In game.m's #implementation:
- (void)dealloc {
// If not using ARC, then be sure to [super dealloc];
[[NSNotificationCenter defaultCenter] removeObserver:self];
}