Is there any Android notifications setContentTitle and setContextText magic values?

I'm currently working on a library with android support.

I'm being asked to notify user on foreground service start. The notification must contain "ApplicationName" as title, and "ApplicationName is running" as text. The notification icon has to be the same as the launcher one.

The target API level is 26.

The notification did not work because the previous developper forgot to open the notification chanel. This is now fixed, we have the notification that pops correctly. And the label are matching expectation.

But now i'm questioning why the notification contains the expected values. I could not find any reference in the javadoc. The following code will display the notification as expectecd the application's name as title and the text "ApplicationName is running" :

@Override
public void onCreate() {
    NotificationChannel channel = new NotificationChannel("APPLICATION_CHANNEL", "MyService", NotificationManager.IMPORTANCE_LOW);
    channel.setDescription(notificationChannelText);
    //block below useful for head up notification
    channel.setSound(null, null);
    channel.setShowBadge(false);
    channel.enableLights(false);
    channel.enableVibration(false);

    NotificationManager notificationManager = (NotificationManager) getApplicationContext().getSystemService(Context.NOTIFICATION_SERVICE);
    notificationManager.createNotificationChannel(channel);
}
@Override
public int onStartCommand(final Intent intent, final int flags, final int startId) {
    foregroundNotification();
    return Service.START_STICKY;
}
/**
 * In order to start foreground service we and generate a service running notification.
 */
private void foregroundNotification() {
    Context context = getApplicationContext();
    Intent notificationIntent = new Intent(context, getClass());
    PendingIntent pendingIntent = PendingIntent.getActivity(context, 0, notificationIntent, 0);
    Notification notification = new Notification.Builder(context, "APPLICATION_CHANNEL")
            .setContentTitle("Title")
            .setContentText("Subject")
            .setContentIntent(pendingIntent)
            .build();
    startForeground(42666, notification);
}

Why doesn't it just display a notification with "Title" as the title and "Subject" as content ?

Are there any constants or magic values that we have to know ?

Where can we find any documentation or definition about it ?

Edit 2020/04/01 : Added code representing notification channel creation

Solution

I found your problem. This is result of your code:

and after add small icon:

.setSmallIcon(R.mipmap.ic_launcher)

It works fine