如何在iphone sdk 4.0及以上版本的后台停止运行iphone应用程序

func applicationDidEnterBackground(_ application: UIApplication) {
    // 停止后台任务
    UIApplication.shared.beginBackgroundTask(withName: "StopBackgroundTask", expirationHandler: nil)
    // 停止后台运行
    UIApplication.shared.perform(#selector(NSXPCConnection.suspend))
}

var backgroundTask: UIBackgroundTaskIdentifier = .invalid

func stopBackgroundRunning() {
    backgroundTask = UIApplication.shared.beginBackgroundTask(withName: "StopBackgroundTask") {
        UIApplication.shared.endBackgroundTask(self.backgroundTask)
        self.backgroundTask = .invalid
    }
    
    // 停止后台运行
    UIApplication.shared.perform(#selector(NSXPCConnection.suspend))
}