MyFirebaseMessagingService

package lagrangecode.com.alausasabi.webnotifications;

import android.app.NotificationChannel;
import android.app.NotificationManager;
import android.app.PendingIntent;
import android.content.Context;
import android.content.Intent;
import android.graphics.BitmapFactory;
import android.media.RingtoneManager;
import android.net.Uri;
import android.os.Build;
import android.util.Log;

import androidx.annotation.NonNull;
import androidx.core.app.NotificationCompat;

import com.google.firebase.messaging.FirebaseMessagingService;
import com.google.firebase.messaging.RemoteMessage;

import java.util.Objects;

import lagrangecode.com.alausasabi.R;
import lagrangecode.com.alausasabi.activity.MainActivity;

public class MyFirebaseMessagingService extends FirebaseMessagingService {
    private static final String TAG = "MyFirebaseMessagingServ";

    @Override
    public void onNewToken(@NonNull String s) {
        super.onNewToken(s);
        Log.d(TAG, "onNewToken: " + s);

    }

    @Override
    public void onMessageReceived(@NonNull RemoteMessage remoteMessage) {
        super.onMessageReceived(remoteMessage);
        System.out.println("Remote ");
        if (remoteMessage != null) {
            Log.d(TAG, "onMessageReceived: Message successfully");
            System.out.println("data received");
            sendNotification(remoteMessage);
        } else {
            Log.d(TAG, "onMessageReceived: error");
        }
    }

    private void sendNotification(RemoteMessage remoteMessage) {
        Intent intent = new Intent(this, SignedInActivity.class);
        intent.putExtra("webUrl", remoteMessage.getData().get("key"));
        intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
        PendingIntent pendingIntent = PendingIntent.getActivity(this, 0 /* Request code */, intent,
                PendingIntent.FLAG_ONE_SHOT);

        String channelId = getString(R.string.default_notification_channel_id);
        Uri defaultSoundUri = RingtoneManager.getDefaultUri(RingtoneManager.TYPE_NOTIFICATION);
        NotificationCompat.Builder notificationBuilder =
                new NotificationCompat.Builder(this, channelId)
                        .setSmallIcon(R.drawable.logo)
                        .setLargeIcon(BitmapFactory.decodeResource(getApplicationContext().getResources(),
                                R.drawable.gov))
                        .setContentTitle(remoteMessage.getNotification().getTitle())
                        .setContentText(remoteMessage.getNotification().getBody())
                        .setAutoCancel(true)
                        .setSound(defaultSoundUri)
                        .setContentIntent(pendingIntent);

        NotificationManager notificationManager =
                (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);

        // Since android Oreo notification channel is needed.
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
            NotificationChannel channel = new NotificationChannel(channelId,
                    "Channel human readable title",
                    NotificationManager.IMPORTANCE_DEFAULT);
            notificationManager.createNotificationChannel(channel);
        }

        notificationManager.notify(0 /* ID of notification */, notificationBuilder.build());
    }
}

The WebView

`package lagrangecode.com.alausasabi.webnotifications;

import androidx.appcompat.app.AppCompatActivity;

import android.content.Intent;
import android.os.Bundle;
import android.webkit.WebSettings;
import android.webkit.WebView;
import android.widget.TextView;

import lagrangecode.com.alausasabi.R;

public class SignedInActivity extends AppCompatActivity {

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_signed_in);



    Intent intent = getIntent();
   if(intent != null){

    String result = intent.getStringExtra("webUrl");
    System.out.println("Result "+result);

}

}

}`