[Bug] Android Push Notifications Not Routing to Notification Channel

[geekywarrior]

Description

I'm developing a .NET Maui Program to interface with Firebase Push Notifications. I'm using version 3.2.11 of Plugin.FirebasePushNotifications

I created a NotificationChannelFactory.cs that iterates through some channel properties I created that are shared with the cloud app that runs firebase.

 public static NotificationChannelRequest[] GetChannels()
        {
            List<NotificationChannelRequest> channels = new();

            foreach(var channel in CustomChannels.GetChannels())
            {
                var request = new NotificationChannelRequest
                {
                    ChannelId = channel.Id,
                    ChannelName = channel.Name,
                    Description = channel.Description,
                    LockscreenVisibility = Android.App.NotificationVisibility.Private,
                    Importance = (Android.App.NotificationImportance) channel.Importance,
                    IsDefault = channel.Id == CustomChannels.DEFAULT_CHANNEL_ID,

                };
                channels.Add(request);
            }


            return channels.ToArray();
        }

In MauiProgram.cs I have the following code to set up the push notifications and map the channels to my list of channels

                .UseFirebasePushNotifications(o =>
                {
#if ANDROID
                    o.Android.NotificationActivityType = typeof(MyMauiApp.MainActivity);
                    o.Android.DefaultNotificationImportance = Android.App.NotificationImportance.Default;
                    o.Android.NotificationChannels = NotificationChannelFactory.GetChannels();

On my main app page, I do call the following

await this.FirebasePushNotification.RegisterForPushNotificationsAsync();
this.FirebasePushNotification.SubscribeTopic(MyMainTopic);
for each(var topic in allTopics)
{
  this.FirebasePushNotification.SubscribeTopic(topic);  
}
FirebasePushNotification.NotificationReceived += HandlePushNotificationOnMainPage;

So far Push Notifications flow into the app appropriately. If in the Foreground the event handler receives the push. If in the background the Android UI displays the notification.

However, if I push to a specified Channel ID, it always goes to the default Channel.
I can look in the android app notification settings and I do see my custom channels, but the default is the only one that shows notifications. If I turn default off, I stop getting notifications. My goal is to allow the user to switch off certain channels and my app assign custom sounds per channel.

If I go into that Event Handler in the Foreground (HandlePushNotificationOnMainPage), and put a breakpoint when it's called and look at the contents of FirebasePushNotificationDataEventArgs e

I do see the Key "gcm.notification.android_channel_id" does have the correct value for the channel id and matches the one on the app side.

So for example, I have something similar to
Id: default, Name: Default Channel
Id: custom_1, Name: Custom Channel 1
Id: custom_2, Name: Custom Channel 2

And if I send a push notification via firebase with this Android Config with the ChannelId of custom_1, I see gcm.notification.android_channel_id does have custom_1 as the value, but it still goes to the Default Channel.

I can try to make a stub project if needed, but am I missing any steps in the configuration?

[thomasgalliker]

I‘ll try what you described using the sample app. Thanks for the good level of details!

[geekywarrior]

Found the issue, in Constants.cs, the Channel ID Key needs to be updated due to Firebase changes on their end

        //Old Channel ID Key
        //public const string ChannelIdKey = "channel_id";
        //FCM now uses prefix gcm.notification.android_ for certain fields
        public const string ChannelIdKey = "gcm.notification.android_channel_id";

That bit me on my own code with getting the title/body from the notifications. Not sure when Firebase changed these keys, must have been recently. Let me know if you want me to make an official pull request and I'll put that together.

I appreciate the support and this project! I was having a hell of a time getting push notifications to work before I found your project.

Partially unrelated, but I'm still having trouble defining the sounds for the Notification Channel.
Right now I'm putting .wav files in Resources/Raw/Media, marking their build action as MauiAsset

I'm mapping the sound in my Channel builder with the following code:

Android.Net.Uri? soundUri = string.IsNullOrEmpty(channel.Sound) ? null : Android.Net.Uri.Parse($"raw/Media/{Path.GetFileName(channel.Sound)}");

It's working in the sense that under the App Settings and Notifications it does say App Defined sound with the file name but never plays. Not too crucial, I'll keep plugging away or dump it if I can't get it to work. Having the channels work at all was the main thing I needed.

[geekywarrior]

Instructions to make the sounds work

• Sounds should go in Platforms\Android\Resources\raw
• Build Action AndroidResource
• No Copy to Output Directory Option Selected
• all lowercase file name (might not be necessary)
• any changes require a full uninstall of the app from the target device due to the notification channel not being deleted between versions. Changes to a channel are not reflected if the channel is already created.
• Code inspiration taken from https://www.reddit.com/r/dotnetMAUI/comments/1g0lpme/custom_ringtone_for_push_notifications_android_is/

public Android.Net.Uri? GenerateSoundUri(string soundFileName)
{
  //Early return if filename is blank/null
  if(string.IsNullOrWhiteSpace(soundFileName) return null;
 
  Android.Net.Uri? soundUri = null;
  int soundResourceId = 0;

  //Try to find the resource id from the filename
  soundResourceId = Android.App.Application.Context.Resources?.GetIdentifier(Path.GetFileNameWithoutExtension(soundFileName), "raw", Android.App.Application.Context.PackageName) ?? 0;
  if (soundResourceId > 0)
  {
    //If it was found, parse into an Android Sound Uri to put into a NotificationChannelRequest
     soundUri = Android.Net.Uri.Parse($"android.resource://{Android.App.Application.Context.PackageName}/{soundResourceId}");
  }

  return soundUri;
}