Xamarin Android 通知未在前台显示

Question

我正在使用 Azure 集线器发送通知。 当我下拉通知 window 时，我能够收到通知并显示在设备上。 但是，我没有按预期在屏幕顶部看到通知显示。 我什至“锁定”了屏幕，但它没有显示。 我收到了通知声音，我的日志显示我收到了它。

显示收到通知的屏幕

我的 FirebaseMessageService：

using System;
using System.Linq;
using WindowsAzure.Messaging;
using Android.App;
using Android.Content;
using Android.Support.V4.App;
using Android.Util;
using Firebase.Messaging;
using IDEQ.AQI.Pages;

namespace IDEQ.AQI.Droid
{
    [Service]
    [IntentFilter(new[] { "com.google.firebase.MESSAGING_EVENT" })]
    public class FirebaseService : FirebaseMessagingService
    {
        const string Tag = "FirebaseMsgService";

        public override void OnNewToken(string token)
        {
            // NOTE: save token instance locally, or log if desired

            SendRegistrationToServer(token);
        }

        private void SendRegistrationToServer(string token)
        {
            try
            {
                var hub = new NotificationHub(Constants.NotificationHubName, Constants.ListenConnectionString, this);

                // register device with Azure Notification Hub using the token from FCM
                var registration = hub.Register(token, Constants.SubscriptionTags);

                // subscribe to the SubscriptionTags list with a simple template.
                var pnsHandle = registration.PNSHandle;
                var templateReg = hub.RegisterTemplate(pnsHandle, "defaultTemplate", Constants.FCMTemplateBody, Constants.SubscriptionTags);
            }
            catch (Exception e)
            {
                Log.Error(Constants.DebugTag, $"Error registering device: {e.Message}");
            }
        }

        public override void OnMessageReceived(RemoteMessage message)
        {
            base.OnMessageReceived(message);
            string messageBody;


            Log.Info(Tag, "From: " + message.From);

            if (message.GetNotification() != null)
            {
                Log.Info(Tag, "Notification Message Body: " + message.GetNotification().Body);
                messageBody = message.GetNotification().Body;
            }

            // NOTE: test messages sent via the Azure portal will be received here
            else
            {
                messageBody = message.Data.Values.First();
            }

            // convert the incoming message to a local notification
            SendLocalNotification(messageBody);

            // send the incoming message directly to the MainPage
            SendMessageToMainPage(messageBody);
        }

        private void SendLocalNotification(string body)
        {
            try
            {
                var intent = new Intent(this, typeof(MainActivity));
                intent.AddFlags(ActivityFlags.ClearTop);
                intent.PutExtra("message", body);

                var requestCode = new Random().Next();
                var pendingIntent = PendingIntent.GetActivity(this, requestCode, intent, PendingIntentFlags.OneShot);

                var notificationBuilder = new NotificationCompat.Builder(this, Constants.NotificationChannelId)
                    .SetContentTitle("IDEQ Alert")
                    .SetSmallIcon(Resource.Drawable.ic_launcher)
                    .SetContentText(body)
                    .SetAutoCancel(true)
                    .SetShowWhen(false)
                    .SetContentIntent(pendingIntent);

                var notificationManager = NotificationManagerCompat.From(this);
                notificationManager.Notify(0, notificationBuilder.Build());
            }
            catch (Exception e)
            {
                Log.Error(Tag, e.ToString());
            }
        }

        private void SendMessageToMainPage(string body)
        {
            (Xamarin.Forms.Application.Current.MainPage as MainPage)?.AddMessage(body);
        }
    }
}

//My main activity where I create the channel:

private void CreateNotificationChannel()
{
    if (Build.VERSION.SdkInt < BuildVersionCodes.O)
    {
        // Notification channels are new in API 26 (and not a part of the
        // support library). There is no need to create a notification
        // channel on older versions of Android.
        return;
    }

    var channel = new NotificationChannel(Constants.NotificationChannelId, Constants.NotificationChannelName, NotificationImportance.Default)
    {
        Description = string.Empty
    };

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

Answer 1

只有当应用程序处于后台或关闭时，系统托盘中的通知才会显示。 如果您的应用程序正在运行，您的 OnMessageRecieved 方法将被命中，但是 Android 不会在系统尝试中显示通知。 这就是推送通知的生命周期在 Android 中的工作方式。 当应用程序在前台时，您可以在系统托盘中显示通知的唯一方法是像在 SendLocalNotification 方法中那样强制执行本地通知。