Questions tagged [nsnotificationcenter]
NSNotificationCenter allows to send and register for notifications in the Foundation framework, which is provided by Apple.
nsnotificationcenter
1,587
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633
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Send and receive messages through NSNotificationCenter in Objective-C?
I am attempting to send and receive messages through NSNotificationCenter in Objective-C. However, I haven't been able to find any examples on how to do this. How do you send and receive messages ...
Cathy
462
votes
17
answers
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NSNotificationCenter addObserver in Swift
How do you add an observer in Swift to the default notification center? I'm trying to port this line of code that sends a notification when the battery level changes.
[[NSNotificationCenter ...
- 15.8k
348
votes
44
answers
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Move view with keyboard using Swift
I have an app that has a text field on the lower half of the view.
This means that when I go to type in the text field the keyboard covers the textfield.
How would I go about moving the view upwards ...
- 7,256
169
votes
7
answers
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views
How to pass data using NotificationCenter in swift 3.0 and NSNotificationCenter in swift 2.0?
I'm implementing socket.io in my swift ios app.
Currently on several panels I'm listening to the server and wait for incoming messages. I'm doing so by calling the getChatMessage function in each ...
- 5,749
137
votes
5
answers
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views
How to pass object with NSNotificationCenter
I am trying to pass an object from my app delegate to a notification receiver in another class.
I want to pass integer messageTotal. Right now I have:
In Receiver:
- (void) receiveTestNotification:...
- 4,732
134
votes
13
answers
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How do you create custom notifications in Swift 3?
In Objective-C, a custom notification is just a plain NSString, but it's not obvious in the WWDC version of Swift 3 just what it should be.
- 1,789
107
votes
9
answers
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Android equivalent to NSNotificationCenter
In the process of porting an iPhone application over to android, I am looking for the best way to communicate within the app. Intents seem to be the way to go, is this the best (only) option? ...
- 1,528
85
votes
8
answers
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iOS 11 - Keyboard Height is returning 0 in keyboard notification
I have been using Keyboard notifications without any problem and getting exact height of Keyboard.
- (void)keyboardDidShow:(NSNotification *) notification{
CGSize keyboardSize = [[[notification ...
- 5,158
78
votes
4
answers
39k
views
Posting NSNotification on the main thread
I found the following code snippet which allows NSNotification to be posted on the main thread from any background thread. I would like to know if this is a safe and acceptable practice please?
...
- 20.5k
74
votes
2
answers
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how to use the object property of NSNotificationcenter
Could somebody please show me how to use the object property on NSNotifcationCenter. I want to be able to use it to pass an integer value to my selector method.
This is how I have set up the ...
- 7,788
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votes
6
answers
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views
How to set addObserver in SwiftUI?
How do I add NotificationCenter.default.addObserve in SwiftUI?
When I tried adding observer I get below error
Argument of '#selector' refers to instance method 'VPNDidChangeStatus'
that is not ...
- 5,558
68
votes
6
answers
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Post of NSNotificationCenter causing "EXC_BAD_ACCESS" exception
A UIViewController adds itself to the default center:
[[NSNotificationCenter defaultCenter]
addObserver:self
selector:@selector(editFood)
name:@"editFood"
object:nil];
Then a UITableView ...
- 681
64
votes
4
answers
26k
views
OS X: Detect system-wide keyDown events?
I'm working on a typing-tutor application for Mac OS X that needs to have keystrokes forwarded to it, even when the application is not in focus.
Is there a way to have the system forward keystrokes ...
- 2,805
51
votes
9
answers
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How to receive NSNotifications from UIWebView embedded YouTube video playback
I didn't received any notifications for MPMoviePlayerController. What am I doing wrong?
I use following logic.
I'm begining to play youtube video in UIWebView. UIWebView calls a standard ...
- 12.5k
49
votes
1
answer
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views
How can I listen for all notifications sent to the iOS NSNotificationCenter's defaultCenter?
I want to listen to all notifications dispatched to the defaultCenter. Both public and private. Does anyone know how I can do this?
- 18.9k
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votes
11
answers
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Detecting Network Connectivity Changes using Reachability, NSNotification and Network Link Conditioner in Swift
From iOS 12 you simply use NWPathMonitor which is a line of code (example).
For historic purposes:
I'm trying to integrate network connectivity detection into my app, however it seems that somewhere ...
- 1,428
42
votes
1
answer
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Are NSNotificationCenter events received synchronously or asynchronously?
If a class registers for NSNotificationCenter events of a certain type and another class posts an event of that type, will the code in the receiver execute before (synchronously) or after (...
- 623
39
votes
3
answers
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How to pass a NSDictionary with postNotificationName:object:
I am trying to pass an NSDictionary form a UIView to a UIViewController using NSNotificationCenter. The dictionary works fine at the time the notification is posted, but in the receiving method I am ...
- 10.5k
38
votes
7
answers
40k
views
iOS NSNotificationCenter to check whether the app came from background to foreground
I have a situation in which i have to intialize an object everytime when it comes from background to foreground and that should be using the NSNotificationCenter not with appdelegate because iam ...
- 687
38
votes
7
answers
18k
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NSNotificationCenter : list of observers?
Is it possible to get the list of observers (objects and selectors) for a given notification name? (NSNotificationCenter)
- 1,055
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votes
2
answers
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iOS Remove observer from notification: Can I call this once for all observers? And even if there are none?
I'm registering three observers in most of my view controllers. Some have more, some less but I want to include part of the registration and unregistration process in a parent class. Is there any ...
- 5,707
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votes
4
answers
13k
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How to communicate between iOS App Containing Extension and Extension (not Host App)
TLDR: Is it possible to send realtime messages or notifications between iOS App and it's Extension?
I'm writing an iOS App with an extension that are part of the same App Group and share the same ...
- 11.7k
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votes
5
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Why is my NSNotification its observer called multiple times?
Within an App I make use of several viewcontrollers. On one viewcontroller an observer is initialized as follows:
[[NSNotificationCenter defaultCenter] removeObserver:self name:@"MyNotification" ...
- 1,806
29
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6
answers
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Type 'NSNotification.Name' has no member 'keyboardDidShowNotification'
I'm getting this error with Swift 4.2
Type 'NSNotification.Name' has no member 'keyboardDidShowNotification'
Here is my code:
NotificationCenter.default.addObserver(self, selector: #selector(self....
- 78.5k
29
votes
3
answers
16k
views
What is parameter `object` in NSNotification addObserver:?
One of my class named Message.m is posting a notification with an object sentObject as below
NSDictionary *sentObject = [NSDictionary dictionaryWithObjectsAndKeys:draftData.arr,@"data", nil];
//Post ...
- 6,109
28
votes
2
answers
25k
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Does removeObserver() remove all observers?
Does the following remove all NSNotificationCenter.defaultCenter there were added by name a view?
NotificationCenter.default.removeObserver(self)
If I have the following in the same view of ...
- 44k
28
votes
3
answers
3k
views
CNContactStoreDidChangeNotification is fired multiple times
I am able to observe the CNContactStoreDidChangeNotification when the contact database is changed while the app is in background state. I am pretty sure that only one observer was added to ...
- 281
26
votes
3
answers
18k
views
How to write unit test for NSNotification
I am working in swift, I want to refresh a page so I am sending it using notification, I am posting a notification in one ViewController and adding observer in another and it is working perfectly. ...
- 2,916
26
votes
6
answers
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NSManagedObject's hasChanges is true while changedValues is empty
I am trying to observe individual NSManagedObject changes on NSManagedObjectContextWillSaveNotification:
- (void)managedObjectContextWillSave:(NSNotification *)notification
{
for (NSManagedObject ...
- 10.9k
25
votes
12
answers
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views
How to write Keyboard notifications in Swift 3
I'm trying to update this code to swift 3:
NSNotificationCenter.defaultCenter().addObserver(self, selector: Selector("keyboardWillShow:"), name: UIKeyboardWillShowNotification, object: nil)
...
- 7,738
25
votes
9
answers
12k
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OSX Notification Center Icon
I'm using OSX's Notification Center APIs for the first time and can't seem to figure out how to make my app's icon to show up in the Notification badge.
The default "your app doesn't have an icon" ...
- 1,785
23
votes
3
answers
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How to post and receive an NSNotifications (Objective C) | Notifications (in Swift)?
Is there an easy-to-grock pattern how to send a NSNotification (Objective C) | Notification (in Swift) and how to receive one? Code snippet? The docs write like 150 pages on the topic. Would like to ...
- 45.8k
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votes
7
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thumbnailImageAtTime: now deprecated - What's the alternative?
Until iOS7 update I was using...
UIImage *image = [moviePlayer thumbnailImageAtTime:1.0 timeOption:MPMovieTimeOptionNearestKeyFrame];
...with great success, so that my app could show a still of the ...
- 4,094
23
votes
3
answers
4k
views
NSNotification order of observer notifications
If I have several classes observing a particular NSNotification, in what order are the observers notified when the notification is posted?
- 1,586
23
votes
3
answers
5k
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When to create a custom NSNotificationCenter?
I've been playing about with the NSNotificationCenter and I've been wondering when you would use your own custom notification center rather than the defaultCenter? And what would the advantages of ...
- 9,963
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votes
8
answers
26k
views
How do I check if an UIViewController is currently being displayed?
How do I check if an UIViewController is currently being displayed?
My UIViewControllers are listening for NSNotifications - even if when they are not displayed (ie not shown). So I could have 10 ...
- 4,293
21
votes
3
answers
16k
views
Removing a NSNotificationCenter observer in iOS 5 ARC
I have an iOS 5 ARC-based project, and am having difficulty about where I should be removing the observer for the NSNotificationCenter observations which I have registered within a UIViewController. ...
- 5,300
21
votes
3
answers
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Warning for iOS/iPhone users about duplicate NSNotification observations
This isn't a question so much as a warning to others to save them some time.
NSNotificationCenter on iOS 3/iPhone OS 3 (I'm assuming also Mac OS X and iOS 4) has the following behavior:
If you ...
- 1,318
20
votes
10
answers
47k
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NSNotificationCenter Swift 3.0 on keyboard show and hide
I am trying to run a function when the keyboard shows and disappears and have the following code:
let notificationCenter = NotificationCenter.default
notificationCenter.addObserver(self, selector: #...
- 465
20
votes
3
answers
15k
views
Type 'NSNotification.Name' has no member 'UITextField'
With Swift 4.2, getting following error, that was working fine with Swift 4.
Type 'NSNotification.Name' has no member 'UITextField'
Here is my error code.
NotificationCenter.default.addObserver(...
- 78.5k
20
votes
3
answers
4k
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NSUserNotificationCenter dismiss notification
I'm trying to use the new Mountain Lion NSUserNotificationCenter for my application (which isn't too hard actually). Posting notifications works like a charm via
NSUserNotification *userNotification ...
- 976
19
votes
4
answers
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NSOperation and NSNotificationCenter on the main thread
I have an NSOperation. When it is finished I fire a NSNotificationCenter to let the program know that the NSoperation is finished and to update the gui.
To my understanding listeners to the ...
- 2,065
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votes
4
answers
26k
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Detect rotation changes in iOS
I am making an iOS app that needs to do a little interface rearrangement upon rotation. I am trying to detect this by implementing - (void)orientationChanged:(NSNotification *)note, but this gives me ...
Undo♦
- 25.6k
19
votes
5
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Adding and removing observers to NSNotificationCenter in a UIViewController
Looking at various Apple examples (for example Add Music) in which I see they add observers to the default NSNotificationCenter in viewDidLoad, then remove them in dealloc. This seems dangerous as ...
- 43.3k
19
votes
2
answers
17k
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Observing Changes to a mutable array using KVO vs. NSNotificationCenter
In my model I have an array of objects called events. I would like my controller to be notified whenever a new object is added to events.
I thought that a good way to do this would be use the KVO ...
- 2,287
18
votes
3
answers
12k
views
Is removing a NotificationCenter observer that was created with closure syntax by name adequate?
I have a few notifications that were created using block / trailing closure syntax which look like this:
NotificationCenter.default.addObserver(forName: .NSManagedObjectContextObjectsDidChange, ...
- 19.7k
17
votes
1
answer
556
views
IOS iMessage extension screenshot detection
Please use Swift 4+
NOTE: I am detecting the screenshot while I am within the iMessage extension, not in the standard iMessage view.
Update - I came up with a working solution that checks the photo ...
- 583
16
votes
4
answers
4k
views
In ARC do we need to send removeObserver: explicitly?
Do we have to send removeObserver: explicitly for objects that have been added as observers to an NSNotificationCenter before?
I am bit confused and unable to find the exact answer for this.
Please ...
- 46.4k
16
votes
5
answers
25k
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Instance was deallocated while key value observers were still registered with it
I've got a UITableView.
Here I got different cell's. Each cell has a model. With KVO and NotificationCenter the cell listen to the model for changes. When I leave the ViewController I get this error:
...
user89862
16
votes
5
answers
3k
views
No EAAccessoryDidConnectNotification and EAAccessoryDidDisconnectNotification after connecting Lightning kBD or Smart KBD
I could not get these two notifications EAAccessoryDidConnectNotification and EAAccessoryDidDisconnectNotification after connecting Lightning kBD or Smart KBD with my APP.
But it worked on iOS9.3 with ...
- 169