Wsrtjtyk

I am new to Android and programming and I am creating an app that receives messages from FCM and its work normally while the app in the Background, so I have added a FirebaseMessagingService class that receives the notifications in onMessageReceived method and followed out google docs but still the notification does not work while the app in the foreground state, I have followed every step and can't figure out where is the problem in my code as the Logs does not help me and I don't receive any bug expect this one which I don't know if its the source if the problem:
Error while parsing timestamp in GCM event java.lang.NumberFormatException: s == null

Here is my MyFirebaseMessagingService class

import android.app.NotificationManager;

import android.app.PendingIntent;

import android.content.BroadcastReceiver;

import android.content.Intent;

import android.support.v4.app.NotificationCompat;

import android.support.v4.app.NotificationManagerCompat;



import com.app.muhammadgamal.swapy.R;

import com.google.firebase.messaging.RemoteMessage;



public class MyFirebaseMessagingService extends com.google.firebase.messaging.FirebaseMessagingService {



    @Override

    public void onMessageReceived(RemoteMessage remoteMessage) {

        super.onMessageReceived(remoteMessage);



        String click_Action = remoteMessage.getNotification().getClickAction();





        String messageTitle = remoteMessage.getNotification().getTitle();

        String messageBody = remoteMessage.getNotification().getBody();





        NotificationCompat.Builder mBuilder = new NotificationCompat.Builder(this, getString(R.string.default_notification_channel_id))

                .setSmallIcon(R.drawable.ic_main_logo)

                .setContentTitle(messageTitle)

                .setContentText(messageBody)

                .setPriority(NotificationCompat.PRIORITY_DEFAULT);





        Intent intent = new Intent(click_Action);

        PendingIntent pendingIntent = PendingIntent.getActivity(this, 0, intent, PendingIntent.FLAG_UPDATE_CURRENT);

        mBuilder.setContentIntent(pendingIntent);





        int mNotificationID = (int)System.currentTimeMillis();

        NotificationManager manager = (NotificationManager)getSystemService(NOTIFICATION_SERVICE);

        manager.notify(mNotificationID,mBuilder.build());



    }

}

and my Manifest File

    <?xml version="1.0" encoding="utf-8"?>

<manifest xmlns:android="http://schemas.android.com/apk/res/android"

    package="com.app.muhammadgamal.swapy">



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

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

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

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



    <application

        android:allowBackup="true"

        android:icon="@drawable/ic_main_logo"

        android:label="@string/app_name"

        android:roundIcon="@drawable/ic_main_logo"

        android:supportsRtl="true"

        android:theme="@style/AppTheme">

        <activity

            android:name=".Activities.SignInActivity"

            android:theme="@style/AppTheme.NoActionBar">

            <intent-filter>

                <action android:name="android.intent.action.MAIN" />



                <category android:name="android.intent.category.LAUNCHER" />

            </intent-filter>

        </activity>

        <activity

            android:name=".Activities.SignUpActivity"

            android:theme="@style/AppTheme.NoActionBar" />

        <activity

            android:name=".Activities.ProfileActivity"

            android:theme="@style/AppTheme.NoActionBar" />

        <activity

            android:name=".Activities.NavDrawerActivity"

            android:theme="@style/AppTheme.NoActionBar" />

        <activity

            android:name=".Activities.SwapCreationActivity"

            android:theme="@style/AppTheme.NoActionBar" />



        <activity android:name=".Activities.ReceivedSwapRequest">

            <intent-filter>

                <action android:name="com.app.muhammadgamal.swapy.Activities.ReceivedSwapRequest_NOTIFICATION_TASK"></action>

                <category android:name="android.intent.category.DEFAULT"></category>

            </intent-filter>

        </activity>



        <service

            android:name=".Notifications.MyFirebaseMessagingService">

            <intent-filter>

                <action android:name="com.google.firebase.MESSAGING_EVENT"/>

            </intent-filter>

        </service>



    </application>



</manifest>

and my index function

   'use strict'





const functions = require('firebase-functions');

const admin = require('firebase-admin');

admin.initializeApp(functions.config().firebase);





exports.sendNotification = functions.database.ref('/Notifications/{receiver_user_id}/{notification_id}')

.onWrite((data, context) =>

{

    const receiver_user_id = context.params.receiver_user_id;

    const notification_id = context.params.notification_id;





    console.log('We have a notification to send to :' , receiver_user_id);





    if (!data.after.val()) 

    {

        console.log('A notification has been deleted :' , notification_id);

        return null;

    }



    const DeviceToken = admin.database().ref(`/Users/${receiver_user_id}/device_token`).once('value');



    return DeviceToken.then(result => 

    {

        const token_id = result.val();



        const payload = 

        {

            notification:

            {

                title: "New Swap Request",

                body: `you have a new Swap Request, Please Check.`,

                click_action: "com.app.muhammadgamal.swapy.Activities.ReceivedSwapRequest_NOTIFICATION_TASK"

            }

        };



        return admin.messaging().sendToDevice(token_id, payload)

        .then(response => 

            {

                return console.log('This was a notification feature.');

            });

    });

});

I discovered the problem, It was that I am using Android O and didn't set the Channel ID for the notification which is a must if you want to receive it on Android 8.0 or higher

so here is the solution code

 private void createNotificationChannel() {

    // Create the NotificationChannel, but only on API 26+ because

    // the NotificationChannel class is new and not in the support library

    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {

        CharSequence name = getString(R.string.channel_name);

        String description = getString(R.string.channel_description);

        int importance = NotificationManager.IMPORTANCE_DEFAULT;

        NotificationChannel channel = new NotificationChannel(CHANNEL_ID, name, importance);

        channel.setDescription(description);

        // Register the channel with the system; you can't change the importance

        // or other notification behaviors after this

        NotificationManager notificationManager = getSystemService(NotificationManager.class);

        notificationManager.createNotificationChannel(channel);

    }

}