服务完成后，android会删除在前台服务中创建的通知

Question

我有一个ForegroundService，它是从BroadcastRevicer开始的，就像这样：

public class AlarmReceiver extends BroadcastReceiver {
    @Override
    public void onReceive(Context context, Intent intent) {
        Log.i("WHD", "Alarm fired!");
        Intent i = new Intent(context, RefreshIntentService.class);
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
            context.startForegroundService(i);
        } else {
            context.startService(i);
        }
    }
}

RefreshIntentService的onCreate如下：

@Override
public void onCreate() {
    super.onCreate();

    createRefreshNotificationChannel();
    NotificationCompat.Builder mBuilder = new NotificationCompat.Builder(this, "notifications_refresh");
    mBuilder.setSmallIcon(R.drawable.ic_notification);
    mBuilder.setContentTitle(getResources().getString(R.string.app_name));
    mBuilder.setPriority(Notification.PRIORITY_MIN);
    mBuilder.setContentText("Refreshing...");

    startForeground(1,mBuilder.build());
}

我现在在服务内部创建其他通知：

private void showNotification(Offer offer) {
    createMainNotificationChannel();
    NotificationCompat.Builder mBuilder = new NotificationCompat.Builder(this, "notifications");
    mBuilder.setSmallIcon(R.drawable.ic_notification);
    mBuilder.setLargeIcon(offer.getBitmap());
    mBuilder.setContentTitle(offer.getName());
    mBuilder.setContentText(getResources().getString(R.string.main_product_available_now) + " " + offer.getPrice());
    mBuilder.setDefaults(Notification.DEFAULT_SOUND);

    Intent i = new Intent(this, OfferDetailsActivity.class);
    i.putExtra("ASIN", offer.getASIN());
    PendingIntent p = PendingIntent.getActivity(this, (int)(Math.random() * 999999), i, PendingIntent.FLAG_CANCEL_CURRENT);
    mBuilder.setContentIntent(p);

    NotificationManager mNotificationManager = (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);
    mNotificationManager.notify(offer.getASIN().hashCode(), mBuilder.build());
}

当服务终止时，Android会自动取消所有在服务内部创建的通知。我该如何预防？