AndroidNotificationRenderer.cs

using System.Collections.Generic;
using System.Threading;
using System.Threading.Tasks;
using Android.App;
using Android.Content;
using Android.OS;
using AndroidX.Core.App;
using AndroidNotification = Android.App.Notification;
using NeuroAccessMaui.Services.Notification;
using System.Text.Json;
using System;
using NeuroAccessMaui;
 
namespace NeuroAccessMaui.Services.Push
{
    public sealed class AndroidNotificationRenderer : INotificationRenderer
    {
        private const string DefaultChannelId = "default";
        private readonly HashSet<string> createdChannels = new HashSet<string>();
 
        public Task RenderAsync(NotificationIntent NotificationIntent, CancellationToken CancellationToken)
        {
            ArgumentNullException.ThrowIfNull(NotificationIntent);
            CancellationToken.ThrowIfCancellationRequested();
 
            if (NotificationIntent.Presentation is NotificationPresentation.StoreOnly or NotificationPresentation.Transient)
            {
                return Task.CompletedTask;
            }
 
            Context? ApplicationContext = Android.App.Application.Context;
            if (ApplicationContext is null)
            {
                return Task.CompletedTask;
            }
            Context ApplicationContextInstance = ApplicationContext;
 
            string ChannelId = string.IsNullOrWhiteSpace(NotificationIntent.Channel) ? DefaultChannelId : NotificationIntent.Channel!;
 
            NotificationManager? NotificationManagerInstance = ApplicationContextInstance.GetSystemService(Context.NotificationService) as NotificationManager;
            if (NotificationManagerInstance is null)
            {
                return Task.CompletedTask;
            }
            NotificationManager NotificationManager = NotificationManagerInstance;
 
            this.EnsureChannel(NotificationManager, ChannelId);
 
            int IconId = ApplicationContextInstance.Resources?.GetIdentifier(
            "ic_stat_appiconfg",
            "drawable",
            ApplicationContextInstance.PackageName) ?? ApplicationContextInstance.ApplicationInfo?.Icon ?? Android.Resource.Drawable.SymDefAppIcon;
            NotificationCompat.Builder? Builder = new NotificationCompat.Builder(ApplicationContextInstance, ChannelId)
                .SetContentTitle(NotificationIntent.Title ?? string.Empty)?
                .SetContentText(NotificationIntent.Body ?? string.Empty)?
                .SetSmallIcon(IconId)?
                .SetAutoCancel(true)?
                .SetPriority((int)NotificationPriority.High);
 
            if (OperatingSystem.IsAndroidVersionAtLeast(26))
            {
                Builder?.SetCategory(AndroidNotification.CategoryMessage);
            }
 
            try
            {
                string Payload = JsonSerializer.Serialize(NotificationIntent);
                Intent LaunchIntent = new Intent(ApplicationContextInstance, typeof(MainActivity));
                LaunchIntent.SetAction(Intent.ActionView);
                LaunchIntent.PutExtra("notificationIntent", Payload);
                LaunchIntent.AddFlags(ActivityFlags.SingleTop | ActivityFlags.ClearTop);
 
                int RequestCode = Math.Abs(Payload.GetHashCode());
                PendingIntent? PendingIntentInstance = PendingIntent.GetActivity(
                    ApplicationContextInstance,
                    RequestCode,
                    LaunchIntent,
                    PendingIntentFlags.UpdateCurrent | PendingIntentFlags.Immutable | PendingIntentFlags.OneShot);
 
                if (PendingIntentInstance is not null)
                {
                    Builder?.SetContentIntent(PendingIntentInstance);
                }
            }
            catch (Exception)
            {
                // If serialization fails, fall back to a notification without tap handling.
            }
 
            if (Builder is null)
                return Task.CompletedTask;
 
            NotificationManager.Notify(Guid.NewGuid().GetHashCode(), Builder.Build());
            return Task.CompletedTask;
        }
 
        private void EnsureChannel(NotificationManager NotificationManagerInstance, string ChannelId)
        {
            if (this.createdChannels.Contains(ChannelId) || !OperatingSystem.IsAndroidVersionAtLeast(26))
                return;
 
            NotificationChannel Channel = new NotificationChannel(ChannelId, ChannelId, NotificationImportance.High)
            {
                LockscreenVisibility = NotificationVisibility.Private
            };
            NotificationManagerInstance.CreateNotificationChannel(Channel);
            this.createdChannels.Add(ChannelId);
        }
    }
}