public Builder setOnlyAlertOnce(boolean onlyAlertOnce) {
            setFlag(Notification.FLAG_ONLY_ALERT_ONCE, onlyAlertOnce);
            return this;
        }
Set this flag if you would only like the sound, vibrate
and ticker to be played if the notification is not already showing.
android/android_framework/base/src/main/java/github/tornaco/android/thanos/core/compat/NotificationCompat.java