MAUI中Foreground模式下NotificationTapped事件未触发的问题

核心原因 #

当应用处于**Foreground（前台）**状态时，FCM不会自动在系统通知栏显示推送通知，用户无法点击通知触发NotificationTapped事件，需手动处理前台通知的接收、显示及点击逻辑。

解决步骤 #

1. 订阅FCM的Received事件并绑定本地通知点击逻辑 #

在App.xaml.cs中新增Received事件订阅，用于捕获前台状态下的通知；同时订阅本地通知的点击事件，将其转发到原有处理逻辑：

public partial class App : Application
{
    public App()
    {
        InitializeComponent();
        CrossFirebaseCloudMessaging.Current.NotificationTapped += Current_NotificationTapped;
        // 订阅FCM通知接收事件（处理前台场景）
        CrossFirebaseCloudMessaging.Current.Received += Current_Received;
        // 订阅本地通知点击事件
        LocalNotificationCenter.Current.NotificationClicked += OnLocalNotificationClicked;
    }

    private void Current_NotificationTapped(object sender, FCMNotificationTappedEventArgs e)
    {
        try
        {
            var data = e.Notification.Data;
            // 处理通知数据与页面跳转逻辑
        }
        catch (Exception ex)
        {
            System.Diagnostics.Debug.WriteLine("Exception:>>" + ex);
        }
    }

    // 处理前台状态下的FCM通知接收
    private void Current_Received(object sender, FCMNotificationReceivedEventArgs e)
    {
        if (Application.Current?.CurrentState == ApplicationState.Active)
        {
            // 构建本地通知请求
            var notificationRequest = new NotificationRequest
            {
                NotificationId = Guid.NewGuid().GetHashCode(),
                Title = e.Notification.Title,
                Description = e.Notification.Body,
                Data = e.Notification.Data,
                Android = new AndroidOptions
                {
                    ChannelId = "fcm_foreground_channel" // 对应后续创建的通知通道ID
                }
            };

            // 发送本地通知到系统通知栏
            _ = LocalNotificationCenter.Current.Show(notificationRequest);
        }
    }

    // 将本地通知点击事件转发到原有处理方法
    private void OnLocalNotificationClicked(object sender, NotificationEventArgs e)
    {
        var fcmArgs = new FCMNotificationTappedEventArgs(new FCMNotification
        {
            Data = e.Request.Data
        });
        Current_NotificationTapped(this, fcmArgs);
    }
}

2. 配置Android通知通道（Android 8.0+ 必需） #

在Android项目的MainApplication.cs中添加通知通道创建逻辑，确保前台通知能正常显示：

using Android.App;
using Android.Content;
using Android.OS;
using Firebase;

namespace YourAppNamespace.Droid;

[Application]
public class MainApplication : MauiApplication
{
    public MainApplication(IntPtr handle, JniHandleOwnership ownership)
        : base(handle, ownership)
    {
    }

    protected override MauiApp CreateMauiApp() => MauiProgram.CreateMauiApp();

    public override void OnCreate()
    {
        base.OnCreate();
        FirebaseApp.InitializeApp(this);
        // 创建前台通知通道
        CreateForegroundNotificationChannel();
    }

    private void CreateForegroundNotificationChannel()
    {
        if (Build.VERSION.SdkInt >= BuildVersionCodes.O)
        {
            var channel = new NotificationChannel(
                "fcm_foreground_channel",
                "FCM前台通知",
                NotificationImportance.Default)
            {
                Description = "用于显示应用前台时的FCM推送通知"
            };

            var notificationManager = (NotificationManager)GetSystemService(NotificationService);
            notificationManager.CreateNotificationChannel(channel);
        }
    }
}

3. 添加Android通知权限 #

在Android项目的AndroidManifest.xml中添加POST_NOTIFICATIONS权限：

<manifest ...>
    <uses-permission android:name="android.permission.POST_NOTIFICATIONS" />
    ...
</manifest>

4. 安装本地通知依赖包 #

通过NuGet安装Plugin.LocalNotification包，用于前台通知的显示与点击处理：

Install-Package Plugin.LocalNotification

说明 #

• 前台状态下，FCM推送先触发Received事件，我们通过该事件创建本地通知并显示在系统通知栏
• 用户点击本地通知时，触发NotificationClicked事件，将其转发到原有的Current_NotificationTapped方法，实现逻辑复用
• 通知通道是Android 8.0及以上版本的强制要求，未配置则通知无法显示

内容的提问来源于stack exchange，提问作者Matthew Pans