I have a UITabBarController with some tab and in all of them i have:
-(void)viewDidappear:(BOOL)animated{
......
[[NSNotificationCenter defaultCenter] addObserverForName:kNotificationName object:nil queue: nil, usingBlock{...}
}
and
-(void)viewDidDisappear:(BOOL)animated{
......
[[NSNotificationCenter defaultCenter] removeObserver:self];
}
In another class i post the notification with name kNotificationName:
[[NSNotificationCenter defaultCenter] postNotification:kNotificationName object:nil];
I've set some log on all of this methods, and the order they are called is correct but...if i switch from First to Second tab (and the notification is posted), the first and the second tab receive the notification (but the viewDidDisappear of the first tab is called!).
If from second tab i go to third tab, the first, second, and third tab receive the notification.
I've tried to use:
[[NSNotificationCenter defaultCenter] removeObserver:self name:postNotification:kNotificationName object:nil];
but the behaviour is the same. All observer are notified.
EDIT1:
As suggest to the other topic i've moved all in viewWillAppear: and viewWillDisappear:, but this haven't have any effect.
I've tried to remove the observer after have received the notification, like this:
-(void)viewWillAppear:(BOOL)animated
{
[super viewWillAppear:animated];
[[NSNotificationCenter defaultCenter] addObserverForName:kDLSyncEngineSyncCompletedNotificationName object:nil queue:nil usingBlock:^(NSNotification *note) {
....
[[NSNotificationCenter defaultCenter] removeObserver:self name:kDLSyncEngineSyncCompletedNotificationName object:nil];
}];
}
But, using this (bad) approach too, the notification is received to the first tab too (i've added this code only on the first tab, to check if after press the second tab, the first tab is receiving again the notification).
EDIT2 - SOLVED - (but what is the difference?)
Instead of using *addObserverForName:object:queue:usingBlock*: I've used *addObserver:selector:name:object:* and in this way all works.
Apple documentation say this for the method with usingBlock:
The block is copied by the notification center and (the copy) held
until the observer registration is removed.
Sure, I've called removeObserver....
Inside the block in the addObserver method -
usingBlock:^(NSNotification *notification){
/*
do something
*/
[[NSNotificationCenter defaultCenter] removeObserver:self];
}];
As you might have already checked this in documentation -
Be sure to invoke removeObserver: or removeObserver:name:object: before notificationObserver or any object specified in addObserver:selector:name:object: is deallocated.
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.
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 the following code within AppDelegate. The purpose being to create a couple of observers, and then call some code. Once that code completes it then posts a notification, and the observer should then remove both observers and call the completion handler.
My issue is that it appears that the observers are not being removed as I expected. The notification is posted, and the NSLog entry is written to console, so I know that the observer is working. However, on the second time of calling, the NSLog is called twice, third time three times etc.
My thoughts are that this is to do with the removal being within the block of code that is running from the observer, however, I am unsure how I can resolve this (if indeed this is what the issue is).
Could someone be so kind as to explain how I can achieve this?
Thanks.
-(void) application:(UIApplication *)application performFetchWithCompletionHandler:
(void (^)(UIBackgroundFetchResult))completionHandler {
[[NSNotificationCenter defaultCenter] addObserverForName:#"fetchDidCompleteNewData" object:nil
queue:nil usingBlock:^(NSNotification *completed) {
//Remove Observers
[[NSNotificationCenter defaultCenter] removeObserver:self
name:#"fetchDidCompleteNewData"
object:nil];
[[NSNotificationCenter defaultCenter] removeObserver:self
name:#"fetchDidCompleteNoData"
object:nil];
// Post completion
completionHandler(UIBackgroundFetchResultNewData);
NSLog(#"Background fetch completed... New Data");
}];
[[NSNotificationCenter defaultCenter] addObserverForName:#"fetchDidCompleteNoData" object:nil
queue:nil usingBlock:^(NSNotification *completed) {
//Remove Observers
[[NSNotificationCenter defaultCenter] removeObserver:self
name:#"fetchDidCompleteNoData"
object:nil];
[[NSNotificationCenter defaultCenter] removeObserver:self
name:#"fetchDidCompleteNewData"
object:nil];
//post completion
completionHandler(UIBackgroundFetchResultNoData);
NSLog(#"Background fetch completed... No New Data");
}];
GetDetails *getDetails = [[GetDetails alloc] init];
[getDetails backgroundRefresh];
}
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
[[UIApplication sharedApplication] setMinimumBackgroundFetchInterval:UIApplicationBackgroundFetchIntervalMinimum];
return YES;
}
You are not registering self as an object. Moreover, when the block is pushed onto the stack by addObserverForName: the method has not yet returned so the notification is nil.
Make a global object using block, eg
__block __weak id notification;
then,
notification = [[NSNotificationCenter defaultCenter] addObserverForName:#"fetchDidCompleteNewData" object:nil queue:nil usingBlock:^(NSNotification *completed) {
//Remove Observers
[[NSNotificationCenter defaultCenter] removeObserver:notification];
}];
My thoughts are that this is to do with the removal being within the
block of code that is running from the observer, however, I am unsure
how I can resolve this (if indeed this is what the issue is).
Could someone be so kind as to explain how I can achieve this?
Certainly.
You can easily test your theory by not using the addObserverForName:object:queue:usingBlock: method and instead using the addObserver:selector:name:object: method, where the selector is the name of a function you call instead of using a block.
Simply use the API guide for NSNotificationCenter for details about these methods, or in general, since you question was about what other method you could use that does not require a block statement, consulting the API is the first place to check for alternative tools within the class.
I'm adding a view controller as an observer for UIKeyboardWillShowNotification notification.
I have this code in my viewDidLoad:
[[NSNotificationCenter defaultCenter] addObserver:self
selector:#selector(keyboardWillShow:)
name:UIKeyboardWillShowNotification
object:nil];
And in my dealloc:
[[NSNotificationCenter defaultCenter] removeObserver:self];
The observer is not being removed even though dealloc is called when the view controller is closed. So when I open it for the second time, NSNotificationCenter will attempt to notify the old object, which is released, and the app crashes.
I have seen several questions here on StackOverflow about this particular problem, but non of the answers works for me.
I've tried removing the observer in viewWillDisappear and viewDidDisappear but the same problem happens.
I'm using ARC.
Have you tried this exact chunk of code in viewWillDisappear?
- (void)viewWillDisappear:(BOOL)animated
{
[super viewWillDisappear:animated];
[[NSNotificationCenter defaultCenter] removeObserver:self];
}
From your explanation I don't think the problem is with the removal of the observer.
Try to trigger the Observer from another viewcontroller. If it's not triggered you'll know the removal is successful and the problem occurs when you are adding the observer the second time.
Maybe try by specifying the parameter name that you have set before like this :
[[NSNotificationCenter defaultCenter] removeObserver:self name:UIKeyboardWillShowNotification object:nil];
Looks like the observer is getting set multiple times. Is your controller inherited from a class which also registers for same notification? That could lead to controller instance getting registered as observer more than once. As a workaround try this, in your controller class where you add the observer,
// Remove as observer first
[[NSNotificationCenter defaultCenter] removeObserver:self];
name:UIKeyboardWillShowNotification
object:nil];
// Then add
[[NSNotificationCenter defaultCenter] addObserver:self
selector:#selector(keyboardWillShow:)
name:UIKeyboardWillShowNotification
object:nil];
This will ensure that the observer is getting added only once.
Hope that helps!
[[NSNotificationCenter defaultCenter] removeObserver:self name:#"name" object:nil];
it works fine with me