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
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)
其他回答
我们也应该删除通知。
Ex.
deinit
{
NotificationCenter.default.removeObserver(self, name:NSNotification.Name(rawValue: "notify"), object: nil)
}
在swift 2.2 - XCode 7.3中,我们为NSNotificationCenter使用#选择器
NSNotificationCenter.defaultCenter().addObserver(self, selector: #selector(rotate), name: UIDeviceOrientationDidChangeNotification, object: nil)
在Swift 5中
我们说如果想从ViewControllerB接收数据到 ViewControllerA
ViewControllerA (Receiver)
import UIKit
class ViewControllerA: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
//MARK: - - - - - Code for Passing Data through Notification Observer - - - - -
// add observer in controller(s) where you want to receive data
NotificationCenter.default.addObserver(self, selector: #selector(self.methodOfReceivedNotification(notification:)), name: Notification.Name("NotificationIdentifier"), object: nil)
}
//MARK: - - - - - Method for receiving Data through Post Notificaiton - - - - -
@objc func methodOfReceivedNotification(notification: Notification) {
print("Value of notification : ", notification.object ?? "")
}
}
视图控制器 B (发射器)
import UIKit
class ViewControllerB: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
//MARK: - - - - - Set data for Passing Data Post Notification - - - - -
let objToBeSent = "Test Message from Notification"
NotificationCenter.default.post(name: Notification.Name("NotificationIdentifier"), object: objToBeSent)
}
}
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
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
}