检测iOS应用程序进入后台

Question

我正在研究用Swift编写的iOS游戏.我试图找到一种方法来检测应用程序何时进入后台模式或因其他原因而中断,例如电话但无法找到任何内容.我该怎么做？

Answer 1

编辑/更新:Xcode 10•Swift 4.2

您可以将观察者添加到视图控制器中 UIApplication.willResignActiveNotification

NotificationCenter.default.addObserver(self, selector: #selector(willResignActive), name: UIApplication.willResignActiveNotification, object: nil)

并向您的视图控制器添加一个选择器方法,该方法将在您的应用收到该通知时执行:

@objc func willResignActive(_ notification: Notification) {
    // code to execute
}

Answer 2

Swift3

let notificationCenter = NotificationCenter.default
    notificationCenter.addObserver(self, selector: #selector(appMovedToBackground), name: Notification.Name.UIApplicationWillResignActive, object: nil)


func appMovedToBackground() {
    print("App moved to background!")
}

Answer 3

用户界面

从背景

Text("Hello, World!")
.onReceive(NotificationCenter.default.publisher(for: UIApplication.willEnterForegroundNotification)) { _ in
    print("To the foreground!")
}

到背景

Text("Hello, World!")
    .onReceive(NotificationCenter.default.publisher(for: UIApplication.willResignActiveNotification)) { _ in
        print("To the background!")
    }

Answer 4

要检测应用程序是否进入后台,您可以在appDelegate.m中查找应用程序委托方法

applicationDidEnterBackground

一旦应用程序进入后台,就会调用此方法.

Answer 5

在Swift 4和iOS 12中：要观察应用程序进入后台事件，请将此代码添加到您的viewDidLoad（）方法中。

    let notificationCenter = NotificationCenter.default
    notificationCenter.addObserver(self, selector: #selector(appMovedToBackground), name: UIApplication.didEnterBackgroundNotification, object: nil)

    @objc func appMovedToBackground() {
        // do whatever event you want
    }

您必须使用UIApplication.didEnterBackgroundNotification。如果您想观察应用程序是否进入前台事件，请使用UIApplication.willEnterForegroundNotification

因此，完整的代码将是：

override func viewDidLoad() {
    super.viewDidLoad()

    let notificationCenter = NotificationCenter.default
    notificationCenter.addObserver(self, selector: #selector(appMovedToBackground), name: UIApplication.didEnterBackgroundNotification, object: nil)

    notificationCenter.addObserver(self, selector: #selector(appCameToForeground), name: UIApplication.willEnterForegroundNotification, object: nil)

    // Do any additional setup after loading the view.
}
 @objc func appMovedToBackground() {
    print("app enters background")
}

@objc func appCameToForeground() {
    print("app enters foreground")
}