How set Firebase notification ChannelID in Android O?

Question

For API level 26 we have to set a channel id as a reference. I learned how to do it without a channelID and below there is my firebase messaging set-up code. But now for the new Android api 26 level

NotificationCompat.Builder(this);

This doesn't work and I should add a reference to channelID as

NotificationCompat.Builder(this, channelID);

But I don't know how to do it. Can you help me to understand how to create a channel ID for Firebase cloud messaging?

AndroidManifest.xml

    <service android:name=".MyFirebaseInstanceIdService">
        <intent-filter>
            <action android:name="com.google.firebase.INSTANCE_ID_EVENT"></action>
        </intent-filter>
    </service>

    <service android:name=".MyFirebaseMessagingService">
        <intent-filter>
            <action android:name="com.google.firebase.MESSAGING_EVENT"></action>
        </intent-filter>
    </service>

MyFirebaseInstanceIdService Java Class:

import android.util.Log;
import com.google.firebase.iid.FirebaseInstanceId;
import com.google.firebase.iid.FirebaseInstanceIdService;

public class MyFirebaseInstanceIdService extends FirebaseInstanceIdService {

    private static final String REG_TOKEN = "REG_TOKEN";

    @Override
    public void onTokenRefresh() {
        String recent_token = FirebaseInstanceId.getInstance().getToken();
        Log.d(REG_TOKEN, recent_token);
    }
}

MyFirebaseMessagingService Java Class

import android.app.Notification;
import android.app.NotificationManager;
import android.app.PendingIntent;
import android.content.Context;
import android.content.Intent;
import android.support.v4.app.NotificationCompat;

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

public class MyFirebaseMessagingService extends FirebaseMessagingService {

    @Override
    public void onMessageReceived(RemoteMessage remoteMessage) {

        Intent intent = new Intent(this, MainActivity.class);
        intent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
        PendingIntent pendingIntent = PendingIntent.getActivity(this, 0, intent, PendingIntent.FLAG_ONE_SHOT);

        // Here I will set up a channel ID as "CH_ID_1" but I do not know how to do this.
        NotificationCompat.Builder notificationBuilder = new NotificationCompat.Builder(this, "CH_ID_1");
        //****************************************************

        notificationBuilder.setContentTitle("FCM NOTIFICATION");
        notificationBuilder.setContentText(remoteMessage.getNotification().getBody());
        notificationBuilder.setAutoCancel(true);
        notificationBuilder.setSmallIcon(R.mipmap.ic_launcher);
        notificationBuilder.setContentIntent(pendingIntent);
        NotificationManager notificationManager = (NotificationManager)getSystemService(Context.NOTIFICATION_SERVICE);
        notificationManager.notify(0, notificationBuilder.build());

    }
}

Gradle - Dependencies

dependencies {
    implementation fileTree(include: ['*.jar'], dir: 'libs')
    implementation 'com.android.support:appcompat-v7:26.1.0'
    implementation 'com.android.support.constraint:constraint-layout:1.1.0'
    implementation 'com.android.support:design:26.1.0'
    testImplementation 'junit:junit:4.12'
    androidTestImplementation 'com.android.support.test:runner:1.0.2'
    androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.2'
    implementation 'com.google.firebase:firebase-core:16.0.0'
    implementation 'com.google.firebase:firebase-messaging:17.0.0'
}
apply plugin: 'com.google.gms.google-services'

Answer 1

What I did in an app before was to initialize the Notification Channels as soon as the app starts. So I added an init function in my Application class, like so:

    @TargetApi(Build.VERSION_CODES.O)
    private void initNotificationChannels() {
        NotificationChannel publicChannel = new NotificationChannel(
                Constants.NOTIFICATION_CHANNEL_PUBLIC,
                Constants.NOTIFICATION_CHANNEL_PUBLIC,
                NotificationManager.IMPORTANCE_DEFAULT);
        publicChannel.setDescription(Constants.NOTIFICATION_CHANNEL_PUBLIC);

        NotificationChannel topicChannel = new NotificationChannel(
                Constants.NOTIFICATION_CHANNEL_TOPIC,
                Constants.NOTIFICATION_CHANNEL_TOPIC,
                NotificationManager.IMPORTANCE_DEFAULT);
        topicChannel.setDescription(Constants.NOTIFICATION_CHANNEL_TOPIC);

        NotificationChannel privateChannel = new NotificationChannel(
                Constants.NOTIFICATION_CHANNEL_PRIVATE,
                Constants.NOTIFICATION_CHANNEL_PRIVATE,
                NotificationManager.IMPORTANCE_HIGH);
        privateChannel.setDescription(Constants.NOTIFICATION_CHANNEL_PRIVATE);
        privateChannel.canShowBadge();

        List<NotificationChannel> notificationChannels = new ArrayList<>();
        notificationChannels.add(publicChannel);
        notificationChannels.add(topicChannel);
        notificationChannels.add(privateChannel);

        NotificationManager mNotificationManager =
                (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);
        if (mNotificationManager != null) {
            mNotificationManager.createNotificationChannels(notificationChannels);
        }
    }

Then in my FirebaseMessagingService, I made a function that gets the channelId when building notifications:

    private String getChannelId(String source) {
        if (!TextUtils.isEmpty(source)) {
            if (source.contains(Constants.TOPIC_PREFIX)) {
                return (TextUtils.equals((TOPIC_PREFIX + Constants.NOTIFICATION_CHANNEL_PUBLIC), source)) ?
                        Constants.NOTIFICATION_CHANNEL_PUBLIC : Constants.NOTIFICATION_CHANNEL_TOPIC;
            } else {
                return Constants.NOTIFICATION_CHANNEL_PRIVATE;
            }
        } else {
            return Constants.NOTIFICATION_CHANNEL_PUBLIC;
        }
    }

This caters to three types of notification that our app needs -- Public, Topic, and Private. You can specify the channels you need on your own.