在你的应用委托中使用下面的代码

import UIKit
import UserNotifications
@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate, UNUserNotificationCenterDelegate {
 var currentToken: String?
 var window: UIWindow?
 func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
        // Override point for customization after application launch.
        application.registerForRemoteNotifications()
        let center = UNUserNotificationCenter.current()
        center.requestAuthorization(options: [.alert, .sound, .badge]) { (granted, error) in

            // Enable or disable features based on authorization.
            if granted == true
            {
                print("Allow")
                UIApplication.shared.registerForRemoteNotifications()
            }
            else
            {
                print("Don't Allow")
            }
        }
        UNUserNotificationCenter.current().delegate = self

        return true
    }
func application(_ application: UIApplication, didRegisterForRemoteNotificationsWithDeviceToken deviceToken: Data){
        let tokenParts = deviceToken.map { data -> String in
            return String(format: "%02.2hhx", data)
        }
        let token = tokenParts.joined()
        currentToken = token  //get device token to delegate variable

    }
 public class var shared: AppDelegate {
        return UIApplication.shared.delegate as! AppDelegate
    }
 func userNotificationCenter(_ center: UNUserNotificationCenter, willPresent notification: UNNotification, withCompletionHandler completionHandler: @escaping (UNNotificationPresentationOptions) -> Void) {
         completionHandler([.alert, .badge, .sound])
    }
}

添加completionHandler行委托方法为我解决了同样的问题:

//Called when a notification is delivered to a foreground app.
@available(iOS 10.0, *)
func userNotificationCenter(_ center: UNUserNotificationCenter, willPresent notification: UNNotification, withCompletionHandler completionHandler: @escaping (UNNotificationPresentationOptions) -> Void) {

completionHandler([.alert, .badge, .sound])
} 

对于任何可能感兴趣的人来说，我最终创建了一个自定义视图，看起来像顶部的系统推送横幅，但添加了一个关闭按钮(小蓝色X)和一个点击消息进行自定义操作的选项。它还支持在用户有时间阅读/删除旧通知之前到达多个通知的情况(没有限制可以堆积多少…)

链接到GitHub: AGPushNote

用法基本上是在线的:

[AGPushNoteView showWithNotificationMessage:@"John Doe sent you a message!"];

在iOS7上看起来是这样的(iOS6有一个iOS6的外观和感觉…)

iOS 14 +

下面这个答案有一个不同之处，.alert已弃用，使用.banner:

class AppDelegate: NSObject, UIApplicationDelegate, UNUserNotificationCenterDelegate {
    func application(
        _ application: UIApplication,
        didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey : Any]? = nil
    ) -> Bool {
        UNUserNotificationCenter.current().delegate = self

        return true
    }

    func userNotificationCenter(
        _ center: UNUserNotificationCenter,
        willPresent notification: UNNotification,
        withCompletionHandler completionHandler: @escaping (UNNotificationPresentationOptions) -> Void
    ) {
        completionHandler([.banner, .badge, .sound])
    }
}

Swift 5

1)使用UNUserNotificationCenterDelegate确认委托到AppDelegate 2)在didFinishLaunch中UNUserNotificationCenter.current().delegate = self 3)在AppDelegate中实现如下方法。

func userNotificationCenter(_ center: UNUserNotificationCenter,
                                willPresent notification: UNNotification,
                                withCompletionHandler completionHandler: @escaping (UNNotificationPresentationOptions) -> Void) {
     print("Push notification received in foreground.")
     completionHandler([.alert, .sound, .badge])
}

就是这样!

Xcode 10 Swift 4.2

当你的应用程序在前台时，显示推送通知

步骤1:在AppDelegate类中添加delegate UNUserNotificationCenterDelegate。

class AppDelegate: UIResponder, UIApplicationDelegate, UNUserNotificationCenterDelegate {

步骤2:设置UNUserNotificationCenter委托

let notificationCenter = UNUserNotificationCenter.current()
notificationCenter.delegate = self

第三步:这一步将允许你的应用程序显示推送通知，即使你的应用程序在前台

func userNotificationCenter(_ center: UNUserNotificationCenter,
                                willPresent notification: UNNotification,
                                withCompletionHandler completionHandler: @escaping (UNNotificationPresentationOptions) -> Void) {
        completionHandler([.alert, .sound])

    }

步骤4:该步骤是可选的。检查你的应用程序是否在前台，如果在前台，然后显示本地推送通知。

func application(_ application: UIApplication,didReceiveRemoteNotification userInfo: [AnyHashable: Any],fetchCompletionHandler completionHandler:@escaping (UIBackgroundFetchResult) -> Void) {

        let state : UIApplicationState = application.applicationState
        if (state == .inactive || state == .background) {
            // go to screen relevant to Notification content
            print("background")
        } else {
            // App is in UIApplicationStateActive (running in foreground)
            print("foreground")
            showLocalNotification()
        }
    }

本地通知功能-

fileprivate func showLocalNotification() {

        //creating the notification content
        let content = UNMutableNotificationContent()

        //adding title, subtitle, body and badge
        content.title = "App Update"
        //content.subtitle = "local notification"
        content.body = "New version of app update is available."
        //content.badge = 1
        content.sound = UNNotificationSound.default()

        //getting the notification trigger
        //it will be called after 5 seconds
        let trigger = UNTimeIntervalNotificationTrigger(timeInterval: 1, repeats: false)

        //getting the notification request
        let request = UNNotificationRequest(identifier: "SimplifiedIOSNotification", content: content, trigger: trigger)

        //adding the notification to notification center
        notificationCenter.add(request, withCompletionHandler: nil)
    }