final int NOTIFY_ID = 1002;
String aMessage="";
String name = "my_package_channel";
String id = "my_package_channel_1"; // The user-visible name of the channel.
String description = "my_package_first_channel"; // The user-visible description of the channel.

Intent intent;
PendingIntent pendingIntent;
NotificationCompat.Builder builder;

if (notifManager == null) {
    notifManager =
            (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);
}

if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
    int importance = NotificationManager.IMPORTANCE_HIGH;
    NotificationChannel mChannel = notifManager.getNotificationChannel(id);
    if (mChannel == null) {
        mChannel = new NotificationChannel(id, name, importance);
        mChannel.setDescription(description);
        notifManager.createNotificationChannel(mChannel);
    }
    builder = new NotificationCompat.Builder(this, id);

    intent = new Intent(this, NotificationReturnSlot.class);
    pendingIntent = PendingIntent.getActivity(this, 1, intent, 0);

    builder.setContentTitle(aMessage)  // required
            .setSmallIcon(R.mipmap.ic_launcher)
            .setContentText(this.getString(R.string.app_name))  // required
            .setAutoCancel(false)
            .setContentIntent(pendingIntent)
            .setVibrate(new long[]{0L})
    ;
} else {

    builder = new NotificationCompat.Builder(this);

    intent = new Intent(this, NotificationReturnSlot.class);
    pendingIntent = PendingIntent.getActivity(this, 1, intent, 0);

    builder.setContentTitle(aMessage)                           // required
            .setSmallIcon(R.mipmap.ic_launcher)
            .setContentText(this.getString(R.string.app_name))  // required
            .setAutoCancel(false)
            .setContentIntent(pendingIntent)
            .setVibrate(new long[]{0L})
            .setPriority(Notification.PRIORITY_HIGH);
}
int mId = 1489;
startForeground(mId, builder.build());