iOS Development UI article-Notification Center (Nsnotificationcenter)

First, Notification Center (Nsnotificationcenter)

Each application has a notification hubs (Nsnotificationcenter) instance that is dedicated to assisting different objects

Communication between the messages

• Any object can publish a notification (nsnotification) to the notification center describing what it is doing. Other objects of interest (Observer) can request to be published at a particular notification (or when a specific object is published)

Ii. Notice (nsnotification)

•

a complete notification typically consists of 3 attributes:-(NSString *) name;//name of the notification- (ID)Object;//notifies the publisher (who wants to post a notification)-(Nsdictionary *) UserInfo;//Some additional information (informing the publisher of the content of the message sent to the notifying recipient)• Initialize a notification (nsnotification) object+ (Instancetype) Notificationwithname: (NSString *) aNameObject:(ID) AnObject; + (Instancetype) Notificationwithname: (NSString *) aNameObject:(ID) AnObject UserInfo: (Nsdictionary *) Auserinfo; -(Instancetype) Initwithname: (NSString *) nameObject:(ID)ObjectUserInfo: (Nsdictionary *) userinfo; A complete notification typically contains 3 attributes:-(NSString *) name;//name of the notification- (ID)Object;//notifies the publisher (who wants to post a notification)-(Nsdictionary *) UserInfo;//Some additional information (informing the publisher of the content of the message sent to the notifying recipient)• Initialize a notification (nsnotification) object+ (Instancetype) Notificationwithname: (NSString *) aNameObject:(ID) AnObject; + (Instancetype) Notificationwithname: (NSString *) aNameObject:(ID) AnObject UserInfo: (Nsdictionary *) Auserinfo; -(Instancetype) Initwithname: (NSString *) nameObject:(ID)ObjectUserInfo: (Nsdictionary *) UserInfo; third, the Announcement Notification Center (Nsnotificationcenter) provides the appropriate method to help publish the notice ·- (void) Postnotification: (nsnotification*) notification; Ø Publish a notification notification, you can set the name of the notification in the notification object, notify the Publisher, additional information, etc. ·- (void) Postnotificationname: (NSString *) Anameobject: (ID) AnObject; Ø Publish a notice called Aname, anobject the publisher of this notice ·- (void) Postnotificationname: (NSString *) aNameObject:(ID) Anobjectuserinfo: (Nsdictionary *) Auserinfo; Ø issued a notice called Aname, AnObject as the publisher of this notice, Auserinfo for additional information four, the registration Notification Listener Notification Center (Nsnotificationcenter) provides a way to register a listener notification of the Listener ( Observer) ·- (void) Addobserver: (ID) Observerselector: (SEL) aselector name: (nsstring*) ANameObject:(ID) AnObject; Øobserver: Listener, that is, who wants to receive this notification Øaselector: After receiving the notification, callback listener this method, and the notification object as a parameter passed in Øaname: the name of the notification. If nil, the listener can receive this notification, regardless of the name of the notification Øanobject: notifies the publisher. If both AnObject and Aname are nil, all notifications are received by the Listener ·- (ID) Addobserverforname: (nsstring*) nameObject:(ID) obj queue: (nsoperationqueue *) Queue usingblock: (void(^) (nsnotification*note)) Block Name: Names of the notifications obj: notifies the publisher Øblock: when a corresponding notification is received, the block queue is called back: determines which operation queue The block executes in, and if nil is passed, the default is to synchronize execution in the current Operation Queue v. Unregister notification Listener · Notification hubs does not hold (retain) listener objects, and objects registered in the notification hub must be unregistered before the object is released. Otherwise, the notification hub will still send a message to the listener when the corresponding notification appears again. Because the corresponding listener object has been freed, it may cause the app to crash • Notification hubs provides a way to unregister listeners o- (void) Removeobserver: (ID) Observer; - (void) Removeobserver: (ID) Observer Name: (NSString *) aNameObject:(IDanobject; generally cancels the registration before the listener destroys it (such as adding the following code to the listener):- (void) Dealloc {//[ Super Dealloc]; this sentence needs to be called in non-arc [[Nsnotificationcenterdefaultcenter] removeobserver:self];The Uidevice informs the Uidevice class that it provides a single-grain object that represents the device through which information about the device can be obtained, such as battery level (batterylevel), battery status (batterystate), type of device ( model, such as ipod, iphone, etc.), device system (systemversion) • This single-grain object can be obtained by [Uidevice Currentdevice] Uidevice object will publish some notifications without interruption, The following is the name constant for the notification published by the Uidevice object: Uideviceorientationdidchangenotification//Device Rotationuidevicebatterystatedidchangenotification//Battery Status Changeuidevicebatteryleveldidchangenotification//Battery charge Changeuideviceproximitystatedidchangenotification//proximity sensors (e.g., the device is close to the user's face)VII. Keyboard Notification • When the system issues keyboard notifications, additional keyboard-related information (dictionaries) is attached, and the dictionary common key is as follows: When the keyboard state changes, the system will issue some specific notifications øuikeyboardwillshownotification//keyboard is about to show Øuikeyboarddidshownotification//Keyboard display Complete øuikeyboardwillhidenotification//keyboard is about to be hidden øuikeyboarddidhidenotification//keyboard hidden Complete øuikeyboardwillchangeframenotification//the position size of the keyboard is about to change øuikeyboarddidchangeframenotification//keyboard position size changedUikeyboardframebeginuserinfokey//the keyboard just started frameUikeyboardframeenduserinfokey//Keyboard final frame (after execution of the animation)Uikeyboardanimationdurationuserinfokey//time of keyboard animationUikeyboardanimationcurveuserinfokey//Keyboard animation execution Rhythm (speed)viii. choice of notification and agent • Common denominator the use of notifications and proxies can accomplish communication between objects (for example, a object tells D objects what happened, a object passes data to D objects) • Different point proxies: one-to-many relationships (an object can only tell what happened to another 1 objects) notification: Many-to-multiple relationships ( 1 objects can tell what happened to n objects, and 1 objects know what happened to n objects .

iOS Development UI article-Notification Center (Nsnotificationcenter)