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
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
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
}
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
}
创建一个objc函数,当通知被调用时执行该函数。
@objc func reloadNotification(_ notification: Notification) {
tblview.reloadData()
}
在didload视图中添加通知观察者。
NotificationCenter.default.addObserver(self, selector:#selector(reloadNotification(_:)), name: Notification.Name("reloadSideMenuDataNS"),object: nil)
将通知发布到想要调用函数的位置。
NotificationCenter.default.post(name: Notification.Name("reloadSideMenuDataNS"), object: nil)
您可以删除您的通知在视图已消失下面。
NotificationCenter.default.removeObserver(self, name: Notification.Name("reloadSideMenuDataNS"), object: nil)
我们也应该删除通知。
Ex.
deinit
{
NotificationCenter.default.removeObserver(self, name:NSNotification.Name(rawValue: "notify"), object: nil)
}