Below is what I have.
MainViewController.m
- (IBAction)sideMenuAction:(id)sender {
NSLog(#"login==sideMenuAction");
[[NSNotificationCenter defaultCenter] postNotificationName:#"ShowMySideMenuNotification" object:self];
}
NotificationListener.m
-(void)viewDidLoad {
[[NSNotificationCenter defaultCenter] removeObserver:self name:#"ShowMySideMenuNotification" object:nil];
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(adjustShowMenu) name:#"ShowMySideMenuNotification" object:nil];
}
-(void) adjustShowMenu {
NSLog(#"notification adjustShowMenu=");
}
Now when I click side menu button in MainViewController, what I was expecting is call adjustShowMenu from NotificationListener once, however it is called twice.
Below is the NSLog for the same.
2015-01-20 12:27:30.798 abc[699:169314] login==sideMenuAction
2015-01-20 12:27:30.798 abc[699:169314] notification adjustShowMenu=
2015-01-20 12:27:30.799 abc[699:169314] notification adjustShowMenu=
What I was expecting is
2015-01-20 12:27:30.798 abc[699:169314] login==sideMenuAction
2015-01-20 12:27:30.798 abc[699:169314] notification adjustShowMenu=
Any idea what is going wrong?
Note: I also tried in viewDidAppear instead of viewDidLoad, but its giving same result.
When I searched online, many answers asked to removeObserver. I did same, but still twice notification is getting called.
As per answer here, I make changes as below and its working fine now.
-(void) viewWillAppear:(BOOL)animated {
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(adjustShowMenu) name:#"ShowMySideMenuNotification" object:nil];
}
-(void) viewWillDisappear:(BOOL)animated {
[[NSNotificationCenter defaultCenter] removeObserver:self name:#"ShowMySideMenuNotification" object:nil];
}
Related
In my custom UITableViewCell I added an observer in NSNotificationCenter:
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(stopActivityIndicator) name:#"stopActivityIndicator" object:nil];
I post a notification in a UIViewController:
[[NSNotificationCenter defaultCenter] postNotificationName:#"stopActivityIndicator" object:nil];
This function "stopActivityIndicator" is not being called, any idea what causes this?
EDIT:
ExploreViewController.m
-(void)showCorrectBannerAfterPlusButtonClicked:(NSNotification *)notification
{
[[NSNotificationCenter defaultCenter] postNotificationName:#"stopActivityIndicator" object:nil];
}
ExploreViewController contains a UITableView with ExploreTableViewCells.
ExploreTableViewCell.m
- (IBAction)plusButtonClicked:(id)sender
{
self.plusButton.hidden = YES;
[self.plusButtonActivityIndicator startAnimating];
[[NSNotificationCenter defaultCenter]addObserver:self selector:#selector(stopActivityIndicator) name:#"stopActivityIndicator" object:nil];
}
-(void)stopActivityIndicator
{
_plusButton.hidden = NO;
[self.plusButtonActivityIndicator stopAnimating];
[[NSNotificationCenter defaultCenter]removeObserver:self name:#"stopActivityIndicator" object:nil];
}
Ok, question, when do you call "showCorrectBannerAfterPlusButtonClicked"?? As this is the method where you post the notification observed by the tableViewCell.
What I see is the notification observer adding and removal, but I don't see how the UIViewController knows when the cell's "plusButtonClicked" is called, so perhaps the method posting the notification is not being called.
Also, be careful with the cell reusage, have in mind if you should remove the observer at that point.
My code:
-(void)viewWillAppear:(BOOL)animated {
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(handleKeyboard:) name:UIKeyboardWillChangeFrameNotification object:nil];
}
-(void)viewWillDisappear:(BOOL)animated {
[[NSNotificationCenter defaultCenter] removeObserver:self];
}
-(void)handleKeyboard:(NSNotification*)notification {
NSLog(#"triggered");
}
See:
The disappearing handler is triggered once as normal, but 3 times when appears. Is this a iOS bug?
Possibly not helpful for your problem but you need to be calling [super viewWill… for your overrides.
-(void)viewWillAppear:(BOOL)animated
-(void)viewWillDisappear:(BOOL)animated
From the docs.
If you override this method, you must call super at some point in
your implementation.
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 am using NSNotifiationCenter, like a 1000 other times, and post a notification, but my observers are not hearing it? What gives?
=== THIS IS IN MY TABLEVIEW ===
- (void)viewDidLoad
{
[super viewDidLoad];
[[NSNotificationCenter defaultCenter] addObserver:self
selector:#selector(handleSuccessSocket)
name:kNotificationServiceStartSuccessful
object:self];
[[NSNotificationCenter defaultCenter] addObserver:self
selector:#selector(handleFailedSocketConnection)
name:kNotificationSocketFailedToConnect
object:self];
}
=== THIS IS IN MY SOCKETMANAGER (socket manager is a singleton if that matters) ===
-(void)willStartService {
....
[[NSNotificationCenter defaultCenter] postNotificationName:kNotificationServiceStartSuccessful object:nil];
....
}
I have debugged and viewDidLoad is being called in my view. Yes, my willStartService is being called.
You are registering the TableView only for notifications sent by itself. It should be..
[[NSNotificationCenter defaultCenter] addObserver:self
selector:#selector(handleSuccessSocket)
name:kNotificationServiceStartSuccessful
object:nil];
Try setting object:nil in your -addObserver:selector:name:object method calls. What you're doing is telling Notification Center to ONLY listen for notifications that come from the table view instance.
If you don't want to pass nil you'll have to pass an instance of your socket manager.
Check the Docs:
https://developer.apple.com/library/mac/documentation/Cocoa/Reference/Foundation/Classes/nsnotificationcenter_Class/Reference/Reference.html#//apple_ref/occ/instm/NSNotificationCenter/addObserver:selector:name:object:
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