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
我们也应该删除通知。
Ex.
deinit
{
NotificationCenter.default.removeObserver(self, name:NSNotification.Name(rawValue: "notify"), object: nil)
}
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)
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
}
Swift 5和Xcode 10.2:
NotificationCenter.default.addObserver(
self,
selector: #selector(batteryLevelDidChangeNotification),
name: UIDevice.batteryLevelDidChangeNotification,
object: nil)
在swift 3, Xcode 8.2:-检查电池状态水平
//Add observer
NotificationCenter.default.addObserver(self, selector: #selector(batteryStateDidChange), name: NSNotification.Name.UIDeviceBatteryStateDidChange, object: nil)
//Fired when battery level changes
func batteryStateDidChange(notification: NSNotification){
//perform manipulation here
}
Xcode 8中的Swift 3.0
Swift 3.0已经用结构“包装器类型”取代了许多“字符串类型”的api, NotificationCenter也是如此。通知现在由struct notification标识。名称而不是字符串。参见迁移到Swift 3指南。
以前的用法:
// Define identifier
let notificationIdentifier: String = "NotificationIdentifier"
// Register to receive notification
NSNotificationCenter.defaultCenter().addObserver(self, selector: #selector(YourClassName.methodOfReceivedNotification(_:)), name: notificationIdentifier, object: nil)
// Post a notification
NSNotificationCenter.defaultCenter().postNotificationName(notificationIdentifier, object: nil)
Swift 3.0的新用法:
// Define identifier
let notificationName = Notification.Name("NotificationIdentifier")
// Register to receive notification
NotificationCenter.default.addObserver(self, selector: #selector(YourClassName.methodOfReceivedNotification), name: notificationName, object: nil)
// Post notification
NotificationCenter.default.post(name: notificationName, object: nil)
所有系统通知类型现在都定义为notification . name上的静态常量;例如。uidevicebatteryleveldidchange, . uiapplicationdidfinishlaunching, . uitextfieldtextdidchange等。
您可以扩展通知。使用您自己的自定义通知命名,以便与系统通知保持一致:
// Definition:
extension Notification.Name {
static let yourCustomNotificationName = Notification.Name("yourCustomNotificationName")
}
// Usage:
NotificationCenter.default.post(name: .yourCustomNotificationName, object: nil)