Android 8.1 REALLY Persistent Foreground Service Notification - persistence

Question

I'm updating my Android app to work with 8.1 from 7. It's not mass-market it's the main alerting app for managed devices - so it NEEDS to stay on.
I have a "persistent" notification for my Foreground service, BUT now in 8+ there's a slider to mute my app notifications.
I can see that android system notifications and other apps remove this slider and display message:
"Notifications from this app can't be turned off".
How do I replicate this pattern?
I've read through notification, service, and channel documentation.
I'm already creating a channel with IMPORTANCE_DEFAULT, using setOngoing(true), and calling startForeground() on the service with the persistent notification:
Here's my Service create and start and channel creation to give you the gist:
public static final String CHANNEL_ID = "ForegroundWebsocketNotificationsServiceChannel";
public static final String CHANNEL_NAME = "WCMobility Notifications";
public static final String CHANNEL_DESCRIPTION = "Required notification and update alerts for WCMobility";
#Override
public void onCreate() {
super.onCreate();
noteMgr = (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);
createNotificationChannel(CHANNEL_ID);
}
#Override
public int onStartCommand(Intent intent, int flags, int startId) {
String action = intent.getAction();
notificationBuilder = new NotificationCompat.Builder(this, CHANNEL_ID);
notificationBuilder.setContentTitle("Service Started");
notificationBuilder.setContentText("Not connected, not receiving messages! ");
int notificationIconID = getIconResId(ICON_FILENAME);
notificationBuilder.setSmallIcon(notificationIconID);
notificationBuilder.setOngoing(true);
notificationIntent = new Intent(this, MainActivity.class);
try{ notificationIntent.putExtras(intent.getExtras());
}catch (Exception e){}
PendingIntent pendingIntent = PendingIntent.getActivity(this, 0, notificationIntent, FLAG_UPDATE_CURRENT);
notificationBuilder.setContentIntent(pendingIntent);
Notification notification = notificationBuilder.build();
startForeground(NOTIFICATION_ID, notification);
return START_NOT_STICKY;
}
private void createNotificationChannel(String channelId) {
// 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) {
int importance = NotificationManager.IMPORTANCE_DEFAULT;
NotificationChannel channel = new NotificationChannel(channelId, CHANNEL_NAME, importance);
channel.setDescription(CHANNEL_DESCRIPTION);
// Register the channel with the system; you can't change the importance
// or other notification behaviors after this
noteMgr.createNotificationChannel(channel);
}
}

Answer 1

We learned that you can't fully block the user from turning off notifications, at least not on consumer devices. Our clients use MDMs and Managed Devices where they restrict access to settings pages etc for end users, plus since the app is primary app used on the phone, user base is not inclined to disable it. This has worked out for us. I did have to add a line to my ForegroundService class code to make the notification dismissable when there was no active session:
stopForeground(false);
stopSelf();
and make it persistant again when session resumed.
startForeground(notificationHelper.NOTIFICATION_ID, notification);
This has worked out for us so far.