post-o-notify.java

@TargetApi(26)
    public static class O {
 
        public static final String CHANNEL_ID = 
            String.valueOf(getRandomNumber());
 
        public static void createNotification(Service context) {
            String channelId = createChannel(context);
            Notification notification = 
                buildNotification(context, channelId);
            context.startForeground(
                ONGOING_NOTIFICATION_ID, notification);
        }
 
        private static Notification buildNotification(
            Service context, String channelId) {
            // Create Pending Intents.
            PendingIntent piLaunchMainActivity = 
                getLaunchActivityPI(context);
            PendingIntent piStopService = 
                getStopServicePI(context);
 
            // Action to stop the service.
            Notification.Action stopAction = 
                new Notification.Action.Builder(
                    STOP_ACTION_ICON,
                    getNotificationStopActionText(context),
                    piStopService)
                    .build();
 
            // Create a notification.
            return new Notification.Builder(context, channelId)
                    .setContentTitle(getNotificationTitle(context))
                    .setContentText(getNotificationContent(context))
                    .setSmallIcon(SMALL_ICON)
                    .setContentIntent(piLaunchMainActivity)
                    .setActions(stopAction)
                    .setStyle(new Notification.BigTextStyle())
                    .build();
        }
 
        @NonNull
        private static String createChannel(Service ctx) {
            // Create a channel.
            NotificationManager notificationManager =
                (NotificationManager) 
                ctx.getSystemService(Context.NOTIFICATION_SERVICE);
            CharSequence channelName = "Playback channel";
            int importance = NotificationManager.IMPORTANCE_DEFAULT;
            NotificationChannel notificationChannel =
                new NotificationChannel(
                    CHANNEL_ID, channelName, importance);
            
            notificationManager.createNotificationChannel(
                 notificationChannel);
            return CHANNEL_ID;
        }
    }