.NET MAUI SDKセットアップ

  dotnet add package OneSignalSDK.DotNet

using OneSignalSDK.DotNet;
using OneSignalSDK.DotNet.Core;
using OneSignalSDK.DotNet.Core.Debug;

public App() {
  InitializeComponent();

  // Enable verbose OneSignal logging to debug issues if needed.
  OneSignal.Debug.LogLevel = LogLevel.VERBOSE;

  // OneSignal Initialization
  OneSignal.Initialize("YOUR_APP_ID");

  // RequestPermissionAsync will show the notification permission prompt.
  // We recommend removing the following code and instead using an In-App Message to prompt for notification permission (See step 5)
  OneSignal.Notifications.RequestPermissionAsync(true);

  MainPage = new AppShell();
}

using System;
using Foundation;
using OneSignalSDK.DotNet;
using OneSignalSDK.DotNet.iOS;
using UIKit;
using UserNotifications;

namespace OneSignalNotificationServiceExtension
{
    [Register("NotificationService")]
    public class NotificationService : UNNotificationServiceExtension
    {
        Action<UNNotificationContent> ContentHandler { get; set; }
        UNMutableNotificationContent BestAttemptContent { get; set; }
        UNNotificationRequest ReceivedRequest { get; set; }

        protected NotificationService(IntPtr handle) : base(handle)
        {
            // Note: this .ctor should not contain any initialization logic.
        }

        public override void DidReceiveNotificationRequest(UNNotificationRequest request, Action<UNNotificationContent> contentHandler)
        {
            ReceivedRequest = request;
            ContentHandler = contentHandler;
            BestAttemptContent = (UNMutableNotificationContent)request.Content.MutableCopy();

            NotificationServiceExtension.DidReceiveNotificationExtensionRequest(request, BestAttemptContent, contentHandler);
        }

        public override void TimeWillExpire()
        {
            // Called just before the extension will be terminated by the system.
            // Use this as an opportunity to deliver your "best attempt" at modified content, otherwise the original push payload will be used.

            NotificationServiceExtension.ServiceExtensionTimeWillExpireRequest(ReceivedRequest, BestAttemptContent);

            ContentHandler(BestAttemptContent);
        }
    }
}

cd ios pod install cd ..