I get twice notification on keyboard down and once on keyboard up…
In my class I put notifications for keyboard:
-(id)init… {
…
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(keyboardWillShow:) name:UIKeyboardWillShowNotification object:nil];
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(keyboardWillHide:) name:UIKeyboardWillHideNotification object:nil];
…
}
to do frame adjustment on keyboard slide.
Later during the class work I use 'ABPeoplePickerNavigationController' to select address.
…
ABPeoplePickerNavigationController *userPicker=[[ABPeoplePickerNavigationController alloc] init];
…
[viewController presentModalViewController:userPicker animated:YES];
…
I’ve found that on ‘presentModalViewController’ I get twice ‘UIKeyboardWillHideNotification’ , BUT once ‘UIKeyboardWillShowNotification’ – when the picker goes out.
Pretty strange.
I tried to remove observer for ‘UIKeyboardWillHideNotification’ from the class initialization (to find any double observer declarations). However, after this remove no ‘UIKeyboardWillHideNotification’ notifications at all.
Why I get different amount of notifications on keyboard up and down?
May be I do something wrong?
Thanks.
It is quite common (especially with the *WillDoSomething message) to receive a notification twice though you expected just once.
What you could do to fix the problem is to have a boolean somewhere which stores the state of the UI. For instance, if keyboardUp is false would mean that you already move the UI to the default state.
Related
I'm using the next code to know when a device is plugged in:
- (void)applicationDidBecomeActive:(UIApplication *)application
{
//code...
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(accesoryChanged:) name:EAAccessoryDidConnectNotification object:nil];
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(accesoryChanged:) name:EAAccessoryDidDisconnectNotification object:nil];
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(accesoryChanged:) name:UIScreenDidConnectNotification object:nil];
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(accesoryChanged:) name:UIScreenDidDisconnectNotification object:nil];
EAAccessoryManager *accessoryManager = [EAAccessoryManager sharedAccessoryManager];
[accessoryManager registerForLocalNotifications];
}
- (void)accesoryChanged:(NSNotification*)note;
{
if(note.name == EAAccessoryDidConnectNotification)
{
EAAccessory* accessory = [note.userInfo objectForKey:EAAccessoryKey];
//code...
}
else if(note.name == EAAccessoryDidDisconnectNotification)
{
EAAccessory* accessory = [note.userInfo objectForKey:EAAccessoryKey];
//code...
}
}
And with:
accessory.name
I can get the device's name, but I couldn't find a way to know what kind of device is (i.e: a controller or a HDMI adapter).
Is there any way to get this information?
Thanks in advance.
The EAAccessory object has properties for the manufacturer, modelNumber, and serialNumber. You can also look at the array of protocolStrings to get an idea of the device's capabilities.
When deciding whether to connect to an accessory, you should use the accessory’s declared protocols to make your determination. The protocols associated with an accessory indicate the types of data the accessory is capable of processing. You may use other properties to help you decide whether or not to connect to an accessory but the list of protocols should be the key factor you consider.
How to create that moveable UItextfield that stay in the bottom of the screen and when the keyboard appears it moves to the top of the keyboared in iphone applications? How to do it in Xcode 4.2?
Just like in whatsapp and Skype chat.
I want to use to input string to a table.
You should register the viewController as a listener for Keyboard Notifications. When the keyboard appears a notification is fired with a user dictionary. The dictionary will contain useful information such as keyboard positions relative to the screen to use to animate your textFields frame to a new position. Check out the documents:
http://developer.apple.com/library/ios/#DOCUMENTATION/StringsTextFonts/Conceptual/TextAndWebiPhoneOS/KeyboardManagement/KeyboardManagement.html
Specifically the notifications you want are:
[[NSNotificationCenter defaultCenter] addObserver:self
selector:#selector(keyboardWasShown:)
name:UIKeyboardDidShowNotification object:nil];
[[NSNotificationCenter defaultCenter] addObserver:self
selector:#selector(keyboardWillBeHidden:)
name:UIKeyboardWillHideNotification object:nil];
You'll want to add these in the viewDidLoad in most cases. And don't forget to unregister for the notifications(removeObserver:) later when you done.Such as in the viewDidUnload.
You can use notifications as Hubert mentioned, or you can constantly check to see if the UITextField is the first responder. If it is the first responder, this means that the text field is selected and the one that the keyboard will affect.
-(void)viewDidLoad {
NSTimer *timer = [NSTimer scheduledTimerWithTimeInterval:0.01 target:self selector:#selector(checkTextField) userInfo:nil repeats:YES];
}
-(void)checkTextField {
if (textField isFirstResponder) {
//the text field has been tapped and the keyboard will come up, so animate the text field moving up here
} else {
//the text field is not selected, so it should be in its original position
}
}
I'm not sure the exact reason for it (other than the ambiguity described below), but I've read that multiple observers shouldn't be added to the NSNotificationCenter for the same object. However, I would like to add a second selector/name pair to the same object in the notification center.
I added the first one as follows:
[[NSNotificationCenter defaultCenter] addObserver:self
selector:#selector(method1:)
name:#"method1Notification"
object:nil];
Option 1:
To add the second (like below) would seem to add "self" to the notification center again.
[[NSNotificationCenter defaultCenter] addObserver:self
selector:#selector(method2:)
name:#"method2Notification"
object:nil];
Is this okay? Or, if necessary, is there a way to simply add another selector/name pair to the "self" entry in the default notification center?
Option 2: (Pseudocode)
[[[NSNotificationCenter defaultCenter] mySelfObserver]
addSelector:#selector(method2:)
name:#"method2Notification"
object:nil];
Ambiguity:
It would seem that either way, if it were added a second time, in dealloc: it might need to be removed as an observer twice?
[[NSNotificationCenter defaultCenter] removeObserver:self];
// ... REMOVE IT AGAIN IF OBSERVER ADDED TWICE TO NOTIFICATION CENTER?
Everything you posted ("Option 1") is okay. See the docs:
removeObserver:
Removes all the entries specifying a given observer from the receiver’s dispatch table.
- (void)removeObserver:(id)notificationObserver
You just need to call removeObserver: once; there's a separate removeObserver:name:object: method if you want to remove just a single observance of a specific notification.
I think you're a little confused. It's perfectly fine to add a given observer any number of times, as long as the notifications or objects are different.
If you add an observer multiple times for a single notification/object combo, you will receive multiple notifications -- your notification method will be called once for each time you added the observer. This is usually not desirable, and I think that's the recommendation that you've seen.
You also only need to call removeObserver: once for any observer, no matter how many things it's observing.
- (void)registerForNotifications
{
NSNotificationCenter * noteCenter = [NSNotificationCenter defaultCenter];
[noteCenter addObserver:self
selector:#selector(keyboardWasShown:)
name:UIKeyboardDidShowNotification
object:nil];
[noteCenter addObserver:self
selector:#selector(keyboardWillBeHidden:)
name:UIKeyboardWillHideNotification
object:nil];
// Totally fine up to this point; this object is observing two different
// notifications.
// Now, add two different observations for the same notification, but
// with _different_ objects:
[noteCenter addObserver:self
selector:#selector(fluffyHasReproduced:)
name:RabbitsHaveReproducedNotification
object:MyRabbitFluffy];
[noteCenter addObserver:self
selector:#selector(luckyHasReproduced:)
name:RabbitsHaveReproducedNotification
object:MyRabbitLucky];
// This is fine; the appropriate rabbit notification method will only be
// called when the corresponding rabbit reproduces.
// However...
// This will make luckyHasReproduced: be called _twice_ whenever
// MyRabbitLucky posts RabbitsHaveReproducedNotification
[noteCenter addObserver:self
selector:#selector(luckyHasReproduced:)
name:RabbitsHaveReproducedNotification
object:MyRabbitLucky];
// Further,
// this is probably not what you want. otherRabbitsHaveReproduced: is
// going to be called whenever either Fluffy or Lucky post their
// notifications, too. The nil object acts as a wildcard.
[noteCenter addObserver:self
selector:#selector(otherRabbitsHaveReproduced:)
name:RabbitsHaveReproducedNotification
object:nil];
}
Later, when appropriate (viewWillDisappear:, or viewDidUnload: for view controllers, depending on the nature of the notifications; dealloc for other objects):
- (void) unregisterForNotifications {
// Clear out _all_ observations that this object was making
[[NSNotificationCenter defaultCenter] removeObserver:self];
}
So I have this function inside NotificationManager class.
-(void) postNotificationForClassName:(NSString*)className withObjects:(NSArray*)objects withError:(BOOL)withError
{
notificationName = [NSString stringWithFormat:#"didLoad%#",className];
[[NSNotificationCenter defaultCenter]
postNotificationName:notificationName object:self];
}
now, let's say I have 2 classes , A and B.
from A's method foo() I do the following:
[[NotificationManager sharedManager]
postNotificationForClassName:#"A" withObjects:objects withError:NO]
from B's method goo() I do the following:
[[NotificationManager sharedManager]
postNotificationForClassName:#"A" withObjects:objects withError:NO]
Now, I'm curious what should I do in case I want to listen only to notifications being posted from Class A.
Is this suppose to work ?
[[NSNotificationCenter defaultCenter]
addObserver:self
selector:#selector(didLoadData:)
name:#"didLoadA" object:classAObject];
Cause I'm assuming that when I'm calling
[[NSNotificationCenter defaultCenter]
postNotificationName:notificationName object:self];
and I pass the "self", then the "self" will be the NotificationManager and not the class A or B that called the NotificationManager method.
Am I right or wrong here ? and if I'm right, is there a way to do what I want to accomplish?
Thanks!
self is a special variable, always referring to the object that received the message currently being handled. In NotificationManager's -postNotificationForClassName:withObjects:objectswithError:withError:, self is a NotificationManager (or descendent). As for self in the call to -addObserver:..., it depends on what method the call occurs in.
As you've noticed, -addObserver:... lets you monitor notifications from specific objects. You could use this to monitor messages from As if you use the class A as the object:
[[NSNotificationCenter defaultCenter]
addObserver:self
selector:#selector(didLoadData:)
name:#"didLoadA" object:[A class]];
However, you'll also need to change the notification sender in -postNotificationForClassName:withObjects:objectswithError:withError:.
-(void)postNotificationForClassName:(NSString*)className
withObjects:(NSArray*)objects
withError:(BOOL)withError
from:(id)sender
{
notificationName = [NSString stringWithFormat:#"didLoad%#",className];
[[NSNotificationCenter defaultCenter]
postNotificationName:notificationName object:[sender class]];
}
Hi
white screen is showing if video is not in supported list. and there is no way user to go back to previous screen(navigation bar too not showing).and
when i initialize the MPMoviePlayerController their retain count is increasing to 4.
here is my code
mMPMovieViewCont=[[MPMoviePlayerViewController alloc]initWithContentURL:theURL];
[theURL release];
theURL=nil;
[[NSNotificationCenter defaultCenter] addObserver:self
selector:#selector(movieDidFinishForOS4:)
name:MPMoviePlayerPlaybackDidFinishNotification
object:nil];
[self.navigationController presentMoviePlayerViewControllerAnimated:mMPMovieViewCont];
NSLog(#"%d",[mMPMovieViewCont retainCount]); //**here count is 4**
- (void) movieDidFinishForOS4:(NSNotification*)notification {
mMPMovieViewCont.moviePlayer.initialPlaybackTime=-1.0;
[mMPMovieViewCont dismissMoviePlayerViewControllerAnimated];
[[NSNotificationCenter defaultCenter] removeObserver:self
name:MPMoviePlayerPlaybackDidFinishNotification
object:nil];
NSLog(#"%d",[mMPMovieViewCont retainCount]); //returning 3
[mMPMovieViewCont release];
mMPMovieViewCont = nil;
}
i am using ios4.2
Do not call retainCount. It is useless in production and misleading for debugging.
The retain count is entirely irrelevant to your question, it would seem. I'm not sure I understand exactly what "Hi white screen is showing if video is not in supported list" means, but it sounds like you need to check to see if the video is compatible with the device or on the approved playlist before you start playback?