如何在默认的通知中心中添加一个观察者?我试图移植这行代码,当电池电量变化时发送通知。
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(batteryLevelChanged:) name:UIDeviceBatteryLevelDidChangeNotification object:nil];
如何在默认的通知中心中添加一个观察者?我试图移植这行代码,当电池电量变化时发送通知。
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(batteryLevelChanged:) name:UIDeviceBatteryLevelDidChangeNotification object:nil];
当前回答
这是一个非常简单的自定义通知观察者和post的例子
添加通知观察员
NotificationCenter.default.addObserver(self, selector: #selector(myFunction), name: Notification.Name("CustomeNotificationName"), object: nil)
添加选择器并处理观察者调用
@objc func myFunction(notification: Notification) {
//Write you code
}
在需要时发布通知(观察员)。
NotificationCenter.default.post(name: NSNotification.Name("CustomeNotificationName"), object: "Object", userInfo: ["key":"Value"])
注意:-当你离开屏幕时,你需要删除观察者。如。
override func viewWillDisappear(_ animated: Bool) {
super.viewWillDisappear(animated)
NotificationCenter.default.removeObserver(self);
}
其他回答
我能够做以下之一成功地使用选择器-没有注释任何@objc:
NSNotificationCenter.defaultCenter().addObserver(self,
selector:"batteryLevelChanged:" as Selector,
name:"UIDeviceBatteryLevelDidChangeNotification",
object:nil)
OR
let notificationSelector: Selector = "batteryLevelChanged:"
NSNotificationCenter.defaultCenter().addObserver(self,
selector: notificationSelector,
name:"UIDeviceBatteryLevelDidChangeNotification",
object:nil)
我的xcrun版本显示Swift 1.2,这适用于Xcode 6.4和Xcode 7 beta 2(我认为会使用Swift 2.0):
$xcrun swift --version
Apple Swift version 1.2 (swiftlang-602.0.53.1 clang-602.0.53)
它与Objective-C API相同,但使用了Swift的语法。
Swift 4.2和Swift 5:
NotificationCenter.default.addObserver(
self,
selector: #selector(self.batteryLevelChanged),
name: UIDevice.batteryLevelDidChangeNotification,
object: nil)
如果你的观察者没有从Objective-C对象继承,你必须用@objc作为你的方法的前缀来使用它作为选择器。
@objc private func batteryLevelChanged(notification: NSNotification){
//do stuff using the userInfo property of the notification object
}
参见NSNotificationCenter类参考,与Objective-C api交互
Declare a notification name extension Notification.Name { static let purchaseDidFinish = Notification.Name("purchaseDidFinish") } You can add observer in two ways: Using Selector NotificationCenter.default.addObserver(self, selector: #selector(myFunction), name: .purchaseDidFinish, object: nil) @objc func myFunction(notification: Notification) { print(notification.object ?? "") //myObject print(notification.userInfo ?? "") //[AnyHashable("key"): "Value"] } or using block NotificationCenter.default.addObserver(forName: .purchaseDidFinish, object: nil, queue: nil) { [weak self] (notification) in guard let strongSelf = self else { return } strongSelf.myFunction(notification: notification) } func myFunction(notification: Notification) { print(notification.object ?? "") //myObject print(notification.userInfo ?? "") //[AnyHashable("key"): "Value"] } Post your notification NotificationCenter.default.post(name: .purchaseDidFinish, object: "myObject", userInfo: ["key": "Value"])
iOS 9和OS X 10.11。它不再需要一个 NSNotificationCenter观察者取消注册 收回。更多信息
对于基于块的实现,如果你想在块中使用self,你需要做一个弱-强舞蹈。更多信息
基于块的观察者需要删除更多信息
let center = NSNotificationCenter.defaultCenter()
center.removeObserver(self.localeChangeObserver)
NSNotificationCenter在iOS 11的Swift 4.0中添加了观察者语法
NotificationCenter.default.addObserver(self, selector: #selector(keyboardShow), name: NSNotification.Name.UIKeyboardWillShow, object: nil)
这是为keyboardWillShow通知名称类型。其他类型可以从可用选项中选择
选择器的类型是@objc func,它处理键盘的显示方式(这是你的用户函数)
Swift 4.0 & Xcode 9.0+:
发送(Post)通知:
NotificationCenter.default.post(name: Notification.Name("NotificationIdentifier"), object: nil)
OR
NotificationCenter.default.post(name: Notification.Name("NotificationIdentifier"), object: nil, userInfo: ["Renish":"Dadhaniya"])
得到(获得)通知:
NotificationCenter.default.addObserver(self, selector: #selector(self.methodOfReceivedNotification(notification:)), name: Notification.Name("NotificationIdentifier"), object: nil)
接收到的通知的函数方法处理程序:
@objc func methodOfReceivedNotification(notification: Notification) {}
Swift 3.0 & Xcode 8.0+:
发送(Post)通知:
NotificationCenter.default.post(name: Notification.Name("NotificationIdentifier"), object: nil)
得到(获得)通知:
NotificationCenter.default.addObserver(self, selector: #selector(YourClassName.methodOfReceivedNotification(notification:)), name: Notification.Name("NotificationIdentifier"), object: nil)
接收到的通知的方法处理程序:
func methodOfReceivedNotification(notification: Notification) {
// Take Action on Notification
}
删除通知:
deinit {
NotificationCenter.default.removeObserver(self, name: Notification.Name("NotificationIdentifier"), object: nil)
}
Swift 2.3和Xcode 7:
发送(Post)通知
NSNotificationCenter.defaultCenter().postNotificationName("NotificationIdentifier", object: nil)
得到(获得)通知
NSNotificationCenter.defaultCenter().addObserver(self, selector: #selector(YourClassName.methodOfReceivedNotification(_:)), name:"NotificationIdentifier", object: nil)
接收的通知的方法处理程序
func methodOfReceivedNotification(notification: NSNotification){
// Take Action on Notification
}
对于历史上的Xcode版本…
发送(Post)通知
NSNotificationCenter.defaultCenter().postNotificationName("NotificationIdentifier", object: nil)
得到(获得)通知
NSNotificationCenter.defaultCenter().addObserver(self, selector: "methodOfReceivedNotification:", name:"NotificationIdentifier", object: nil)
删除通知
NSNotificationCenter.defaultCenter().removeObserver(self, name: "NotificationIdentifier", object: nil)
NSNotificationCenter.defaultCenter().removeObserver(self) // Remove from all notifications being observed
接收的通知的方法处理程序
func methodOfReceivedNotification(notification: NSNotification) {
// Take Action on Notification
}
用@objc注释类或目标方法
@objc private func methodOfReceivedNotification(notification: NSNotification) {
// Take Action on Notification
}
// Or
dynamic private func methodOfReceivedNotification(notification: NSNotification) {
// Take Action on Notification
}