Obj-C - NSNotification executing twice? - ios

Question

For some reason, UIKeyboardWillHideNotification is being executed twice in my below code - I haven't a clue as to why. I know this because my NSLog ("Closed!") appears twice in my console. Am I missing something obvious (and no, I don't have UIKeyboardWillHideNotification pasted somewhere in my code a second time).
-(void)viewDidLoad {
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(keyboardWillChange:) name:UIKeyboardWillShowNotification object:nil];
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(handleKeyboard:) name:UIKeyboardWillHideNotification object:nil];
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(handleKeyboard:) name:UIKeyboardWillShowNotification object:nil];
}
- (void)handleKeyboard:(NSNotification*)aNotification{
NSDictionary* info = [aNotification userInfo];
NSValue* value = [info objectForKey:UIKeyboardAnimationDurationUserInfoKey];
NSTimeInterval duration = 3;
[value getValue:&duration];
if (aNotification.name == UIKeyboardWillShowNotification) {
self.upView.frame = CGRectOffset(self.upView.frame, 0, -self.keyboardHeight); self.tableView.frame = CGRectOffset(self.tableView.frame, 0, -self.keyboardHeight);
[self moveCustomView:YES duration:duration];
}
if (aNotification.name == UIKeyboardWillHideNotification) {
/** KEYBOARD HIDE **/
self.upView.frame = CGRectOffset(self.upView.frame, 0, self.keyboardHeight); self.tableView.frame = CGRectOffset(self.tableView.frame, 0, self.keyboardHeight);
[self moveCustomView:NO duration:duration];
NSLog(#"CLOSED!");
}
}

Answer 1

Make sure to remove observers in viewDidDisappear as , view controller may be not reallocated from some reason and code in viewDidLoad is executed twice as observer is added twice
// Objective c
- (void)viewWillDisappear:(BOOL)paramAnimated{
[super viewWillDisappear:paramAnimated];
[[NSNotificationCenter defaultCenter] removeObserver:self name:UIKeyboardWillShowNotification object:nil];
[[NSNotificationCenter defaultCenter] removeObserver:self name:UIKeyboardWillHideNotification object:nil];
}
// Swift
override func viewDidDisappear(_ animated: Bool)
{
NotificationCenter.default.removeObserver(self, name: NSNotification.Name.UIKeyboardDidShow, object: nil)
NotificationCenter.default.removeObserver(self, name: NSNotification.Name.UIKeyboardWillHide, object: nil)
}

Answer 2

Be sure to remove the observer from the dealloc method. If you do not remove it and its memory is not released, it will listen for keyboard behavior on other pages. In addition, you should not add the same notification twice to the same observer.

Answer 3

Instead of Using same method for Hide and show notification. You can use two different Methods.
[[NSNotificationCenter defaultCenter] addObserver:self
selector:#selector(keyboardWasShown:)
name:UIKeyboardDidShowNotification object:nil];
[[NSNotificationCenter defaultCenter] addObserver:self
selector:#selector(keyboardWillBeHidden:)
name:UIKeyboardWillHideNotification object:nil];
Now, for Change your frame You can use following code
NSDictionary* info = [aNotification userInfo];
CGSize *kbSize = [[info objectForKey:UIKeyboardFrameBeginUserInfoKey] CGRectValue].size;
self.tableView.frame = CGRectOffset(self.tableView.frame, 0, -kbSize.height);

Answer 4

Please, try it like this:
What I did:
• moved subscription to viewWillAppear
• added "unsubscribe" in viewWillDisappear
• added "unsubscribe" in dealloc (shouldn't be related to your issue, but that's the right way to do it still)
• replaced == with isEqual in your handler (also not related to your issue, most likely).
There may be some typos there. Sorry, if that's the case.
-(void)viewWillAppear {
[super viewWillAppear];
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(keyboardWillChange:) name:UIKeyboardWillShowNotification object:nil];
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(handleKeyboard:) name:UIKeyboardWillHideNotification object:nil];
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(handleKeyboard:) name:UIKeyboardWillShowNotification object:nil];
}
-(void)viewDidLoad {
[super viewDidLoad];
//Leaving this method here just to point out that everything was moved to viewWillAppear
}
- (void)handleKeyboard:(NSNotification*)aNotification{
NSDictionary* info = [aNotification userInfo];
NSValue* value = [info objectForKey:UIKeyboardAnimationDurationUserInfoKey];
NSTimeInterval duration = 3;
[value getValue:&duration];
if ([aNotification.name isEqual: UIKeyboardWillShowNotification]) {
self.upView.frame = CGRectOffset(self.upView.frame, 0, -self.keyboardHeight);
self.tableView.frame = CGRectOffset(self.tableView.frame, 0, -self.keyboardHeight);
[self moveCustomView:YES duration:duration];
}
if ([aNotification.name isEqual: UIKeyboardWillHideNotification]) {
/** KEYBOARD HIDE **/
self.upView.frame = CGRectOffset(self.upView.frame, 0, self.keyboardHeight);
self.tableView.frame = CGRectOffset(self.tableView.frame, 0, self.keyboardHeight);
[self moveCustomView:NO duration:duration];
NSLog(#"CLOSED!");
}
}
-(void)unsubscribe {
[[NSNotificationCenter defaultCenter] removeObserver:self];
}
-(void)viewWillDisappear {
[super viewWillDisappear];
[self unsubscribe];
}
-(void)dealloc {
[self unsubscribe];
}