Plugin.FirebasePushNotifications 4.0.18-pre

Plugin.FirebasePushNotifications

Plugin.FirebasePushNotifications provides a seamless way to engage users and keep them informed about important events in your .NET MAUI applications. This open-source C# library integrates Firebase Cloud Messaging (FCM) into your .NET MAUI projects, enabling you to receive push notifications effortlessly.

Features

• Cross-platform Compatibility: Works seamlessly with .NET MAUI, ensuring a consistent push notification experience across different devices and platforms.
• Easy Integration: Simple setup process to incorporate Firebase Push Notifications into your .NET MAUI apps.
• Flexible Messaging: Utilize FCM's powerful features, such as targeted messaging, to send notifications based on user segments or specific conditions.

Download and Install Plugin.FirebasePushNotifications

This library is available on NuGet: https://www.nuget.org/packages/Plugin.FirebasePushNotifications Use the following command to install Plugin.FirebasePushNotifications using NuGet package manager console:

PM> Install-Package Plugin.FirebasePushNotifications

You can use this library in any .NET MAUI project compatible to .NET 7 and higher.

Setup

Setup Firebase Push Notifications

• Go to https://console.firebase.google.com and create a new project. The setup of Firebase projects is not (yet?) documented here. Contributors welcome!
• You have to download the resulting Firebase service files and integrate them into your .NET MAUI csproj file. google-services.json is used by Android while GoogleService-Info.plist is accessible to iOS. Make sure the Include and the Link paths match.

<ItemGroup Condition="$(TargetFramework.Contains('-android'))">
	<GoogleServicesJson Include="Platforms\Android\Resources\google-services.json" Link="Platforms\Android\Resources\google-services.json" />
</ItemGroup>

<ItemGroup Condition="$(TargetFramework.Contains('-ios'))">
	<BundleResource Include="Platforms\iOS\GoogleService-Info.plist" Link="GoogleService-Info.plist" />
</ItemGroup>

• iOS apps need to be enabled to support push notifications. Turn on the "Push Notifications" capability of your app in the Apple Developer Portal.

MAUI App Startup

This plugin provides an extension method for MauiAppBuilder UseFirebasePushNotifications which ensure proper startup and initialization. Call this method within your MauiProgram just as demonstrated in the MauiSampleApp:

var builder = MauiApp.CreateBuilder()
    .UseMauiApp<App>()
    .UseFirebasePushNotifications();

UseFirebasePushNotifications has optional configuration parameters which are documented in another section of this document.

Android-specific Setup

• Copy the google-services.json to path location Platforms\Android\Resources\google-services.json (depending on what is configured in the csproj file).
• Make sure your launcher activity (usually this is MainActivity - but not always) uses LaunchMode = LaunchMode.SingleTask. You can also use a different LaunchMode; just be very sure what you do!

iOS-specific Setup

• Copy the GoogleService-Info.plist to path location Platforms\iOS\GoogleService-Info.plist (depending on what is configured in the csproj file).
• Extend the AppDelegate.cs file with following method exports:

[Export("application:didRegisterForRemoteNotificationsWithDeviceToken:")]
[BindingImpl(BindingImplOptions.GeneratedCode | BindingImplOptions.Optimizable)]
public void RegisteredForRemoteNotifications(UIApplication application, NSData deviceToken)
{
    IFirebasePushNotification.Current.RegisteredForRemoteNotifications(deviceToken);
}

[Export("application:didFailToRegisterForRemoteNotificationsWithError:")]
[BindingImpl(BindingImplOptions.GeneratedCode | BindingImplOptions.Optimizable)]
public void FailedToRegisterForRemoteNotifications(UIApplication application, NSError error)
{
    IFirebasePushNotification.Current.FailedToRegisterForRemoteNotifications(error);
}

[Export("application:didReceiveRemoteNotification:fetchCompletionHandler:")]
public void DidReceiveRemoteNotification(UIApplication application, NSDictionary userInfo, Action<UIBackgroundFetchResult> completionHandler)
{
    IFirebasePushNotification.Current.DidReceiveRemoteNotification(userInfo);
    completionHandler(UIBackgroundFetchResult.NewData);
}

API Usage

IFirebasePushNotification is the main interface which handles most of the desired Firebase push notification features. This interface is injectable via dependency injection or accessible as a static singleton instance IFirebasePushNotification.Current. We strongly encourage you to use the dependency injection approach in order to keep your code testable.

The following lines of code demonstrate how the IFirebasePushNotification instance is injected in MainViewModel and assigned to a local field for later use:

public MainViewModel(
    ILogger<MainViewModel> logger,
    IFirebasePushNotification firebasePushNotification)
{
    this.logger = logger;
    this.firebasePushNotification = firebasePushNotification;
}

Notification Permissions

Before we can receive any notification we need to make sure the user has given consent to receive notifications. INotificationPermissions is the service you can use to check the current authorization status or ask for notification permission. You can either inject INotificationPermissions into your view models or access it via the the static singleton instance INotificationPermissions.Current.

• Check the current notification permission status:

this.AuthorizationStatus = await this.notificationPermissions.GetAuthorizationStatusAsync();

• Ask the user for notification permission:

await this.notificationPermissions.RequestPermissionAsync();

Notification permissions are handled by the underlying operating system (iOS, Android). This library just wraps the platform-specific methods and provides a uniform API for them.

Register for Notifications

The main goal of a push notification client library is to receive notification messages. This library provides a set of classic .NET events to inform your code about incoming push notifications. Before any notification event is received, we have to inform the Firebase client library, that we're ready to receive notifications. RegisterForPushNotificationsAsync registers our app with the Firebase push notification backend and receives a token. This token is used by your own server/backend to send push notifications directly to this particular app instance. The token may change after some time. It is not controllable by this library if/when the token is going to be updated. The TokenRefreshed event will be fired whenever a new token is available. See Token property and TokenRefreshed event provided by IFirebasePushNotification for more info.

await this.firebasePushNotification.RegisterForPushNotificationsAsync();

If we want to turn off any incoming notifications, we can unregister from push notifications. The Token can no longer be used to send push notifications to.

await this.firebasePushNotification.UnregisterForPushNotificationsAsync();

Receive Notifications

Following .NET events can be subscribed.

Notification Handling Behavior

The following table documents the behavior of each platform for incoming push notifications. We distinguish between notification message and data message.

• Notification messages must have a notification part with title and/or body. Other sections such as data are optional.
• Data messages must only have a data section (and can have platform specific options). The purpose of this message type is to send data-only messages without displaying a system notification popup.

The behavior when receiving notifications is also different if the app runs in foreground or in background mode. The following table illustrates some use cases with different message types, priority flags and app states.

*) System notification popup: Official name is heads-up notification on Android and banner notification on iOS.

*) Notification channels exist on Android since Android 8.0 (API level 26).

Topics

The most common way of sending push notifications is by targeting notification message directly to push tokens. Firebase allows to send push notifications to groups of devices, so-called topics. If a user subscribes to a topic, e.g. "weather_updates" you can send push notifications to this topic instead of a list of push tokens.

Subscribe to Topic

Use method SubscribeTopicAsync with the name of the topic.

this.firebasePushNotification.SubscribeTopicAsync("weather_updates");

Send Notifications to Topic Subscribers

Use the Firebase Admin SDK (or any other HTTP client) to send a push notification targeting subscribers of the topic "weather_updates". Instead of message property to which addresses an FCM token directly, we use topic to send notification messages to a whole group of subscribed devices.

HTTP POST https://fcm.googleapis.com/v1/projects/{{project_id}}/messages:send

{
    "message": {
        "topic": "weather_updates",
        "notification": {
            "title": "Weather Update",
            "body": "Pleasant with clouds and sun"
        },
        "data": {
            "sunrise": "1684926645",
            "sunset": "1684977332",
            "temp": "292.55",
            "feels_like": "292.87"
        }
    }
}

Notification Actions

Notification actions are special buttons which allow for immediate response to a particular notification. A list of NotificationActions is consolidated within a NotificationCategory.

Register Notification Actions

The following example demonstrates the registration of a notification category with identifier "medication_intake" and two actions "Take medicine" and "Skip medicine":

var categories = new[]
{
    new NotificationCategory("medication_intake", new[]
    {
        new NotificationAction("take_medication", "Take medicine", NotificationActionType.Foreground),
        new NotificationAction("skip_medication", "Skip medicine", NotificationActionType.Foreground),
    })
};

Notification categories are usually registered at app startup time using the following method call:

IFirebasePushNotification.Current.RegisterNotificationCategories(categories);

Subscribe to Notification Actions

Subscribe the event IFirebasePushNotification.NotificationAction to get notified if a user presses one of the notification action buttons. The delivered event args FirebasePushNotificationResponseEventArgs will let you know which action was pressed.

Send Notification Actions

Use the Firebase Admin SDK (or any other HTTP client) to send a push notification with:

HTTP POST https://fcm.googleapis.com/v1/projects/myproject-b5ae1/messages:send

{
    "message": {
        "token": "XXXXXXXXXX",
        "notification": {
            "title": "Medication Intake",
            "body": "Do you want to take your medicine?"
        },
        "data": {
            "priority": "high"
        },
        "android": {
            "notification": {
                "click_action": "medication_intake"
            }
        },
        "apns": {
            "payload": {
                "aps": {
                    "category": "medication_intake"
                }
            }
        }
    }
}

If everything works fine, the mobile device with the given token displays the notification action as follows:

Notification Channels

Notification channels are an Android feature introduced in Android 8.0 (API level 26) that let users manage notification settings for different categories of notifications within the app. Each notification channel represents a distinct type of notification (such as chat messages, medication intake, or promotions) and allows users to customize notification preferences per channel, rather than for the whole app.

Default Notification Channel

Your app must always have at least one notification channel. This library will use this channel for any notifications that are not targeting a specific channel. This ensures that push notifications are delivered even if a custom channel is not set up.

It is highly recommended to create the default notification channel by yourself so that all properties are under your control. Use INotificationChannels.Channels methods to create notification channels manually at startup or specify them in the Android-specific options under UseFirebasePushNotifications(o => o.Android.NotificationChannels = ...)). To get an idea of how to use the NotificationChannels option, take a look at MauiProgram.cs in the sample app in this repository.

Notification Channel Importance

When your app (or this library) creates a notification channel, you must specify its importance (e.g., Low, Default, High). Importance controls how notifications are presented (such as whether they make a sound or appear as a heads-up notification).

Notification Channel Groups

Multiple notification channels may be grouped together within a notification channel group. Use INotificationChannels.ChannelGroups methods to create/delete notification channel groups.

More Push Notification Scenarios

There are a lot of features in this library that can be controlled via specific data flags. The most common scenarios are end-to-end tested with the MauiSampleApp using postman calls. You can find an up-to-date postman collection in this repository.

• Import the collection in postman.
• Adjust the variables, especially the project_id and the fcm_token accordingly.
• Get a Bearer authentication token either by selecting the Auth Type "Firebase Cloud Messaging API (Oauth 2.0)" or by creating it manually via https://developers.google.com/oauthplayground (see this youtube video).

Options

to be documented

Contribution

If you find a bug or want to propose a new feature, feel free to create a new issue here. Please use the predefined issue templates when submitting a new issue.

Thank You

Your contribution is valuable! Open source software isn’t just something you can pick up for free — it represents the hard work and dedication of many people who often not even know each other. We sincerely appreciate the time, effort, and dedication shown by everyone who helps keep this plugin going forward.

Links

• FCM messages, data format, concepts and options:

  https://firebase.google.com/docs/cloud-messaging/concept-options

• Set up a Firebase Cloud Messaging client app on Apple platforms:

  https://firebase.google.com/docs/cloud-messaging/ios/client

• Set up a Firebase Cloud Messaging client app on Android:

  https://firebase.google.com/docs/cloud-messaging/android/client

• Expandable notification on Android:

  https://developer.android.com/develop/ui/views/notifications/expanded

• Create bearer authentication tokens for Firebase Cloud Messaging (and other Google APIs):

  https://developers.google.com/oauthplayground