Foreground service stops working when the main application has been closed

[software.it]

Hi,
I'm working on android 7.0 and I'm trying to write an android service using Qt.
Basically what I'm trying to do is a simple service who replies to commands received on ZMQ and for this task I'm using a foreground service since I want that the service continues to run even if the application that has started it has been closed.

This is my java service:

public class QtAndroidService extends Service
{
    private static final String TAG = "QtAndroidService";
    private Notification.Builder serviceNotificationBuilder         = null;
    private static native void startZMQ();

    @Override
    public void onCreate() {
        super.onCreate();
        NotificationManager notification_manager =
                        (NotificationManager)getSystemService(Context.NOTIFICATION_SERVICE);
                if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
                    NotificationChannel channel = new NotificationChannel(getResources().getString(R.string.service_notification_channel_id),
                            getResources().getString(R.string.service_notification_channel_name),
                            NotificationManager.IMPORTANCE_LOW);

                    channel.setShowBadge(false);

                    notification_manager.createNotificationChannel(channel);

                    serviceNotificationBuilder = new Notification.Builder(this, getResources().getString(R.string.service_notification_channel_id))
                            .setSmallIcon(R.drawable.ic_stat_notify_service)
                            .setContentTitle(getResources().getString(R.string.service_notification_title))
                            .setContentText(getResources().getString(R.string.service_notification_text));
                            //.setContentIntent(PendingIntent.getActivity(this, 0, new Intent(this, MainActivity.class), 0));
                } else {
                    serviceNotificationBuilder = new Notification.Builder(this)
                            .setPriority(Notification.PRIORITY_LOW)
                            .setSmallIcon(R.drawable.ic_stat_notify_service)
                            .setContentTitle(getResources().getString(R.string.service_notification_title))
                            .setContentText(getResources().getString(R.string.service_notification_text));
                            //.setContentIntent(PendingIntent.getActivity(this, 0, new Intent(this, MainActivity.class), 0));
                }

                startForeground(getResources().getInteger(R.integer.service_foreground_notification_id), serviceNotificationBuilder.build());
    }

    @Override
    public void onDestroy() {
        super.onDestroy();
        Log.i(TAG, "Destroying Service");
    }

    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        super.onStartCommand(intent, flags, startId);
        new Thread(new Runnable() {
                        public void run() {
                            startZMQ();
                        }
                    }).start();


        return Service.START_STICKY;
    }

    @Override
    public IBinder onBind(Intent intent) {
        return null;
    }
}

I started the service in this way

JNINativeMethod methods[] {{"startZMQ", "()V", reinterpret_cast<void *>(startZMQ)}};
    QAndroidJniObject javaClass("org/qtproject/example/qtandroidservice/QtAndroidService");

    QAndroidJniEnvironment env;
    jclass objectClass = env->GetObjectClass(javaClass.object<jobject>());
    env->RegisterNatives(objectClass,
                         methods,
                         sizeof(methods) / sizeof(methods[0]));
    env->DeleteLocalRef(objectClass);

    QAndroidIntent serviceIntent(QtAndroid::androidActivity().object(),
                                        "org/qtproject/example/qtandroidservice/QtAndroidService");
    //serviceIntent.putExtra("name", name.toUtf8());
    QAndroidJniObject result = QtAndroid::androidActivity().callObjectMethod(
                "startService",
                "(Landroid/content/Intent;)Landroid/content/ComponentName;",
                serviceIntent.handle().object());

and this is the zeromq server function:

static void startZMQ(JNIEnv *env, jobject /*thiz*/)
{
        void *context = zmq_ctx_new ();
        void *responder = zmq_socket (context, ZMQ_REP);
        int rc = zmq_bind (responder, "tcp://*:5555");
        assert (rc == 0);

        while (1) {
            char buffer [10];
            zmq_recv (responder, buffer, 10, ZMQ_NOBLOCK);
            printf ("Received Hello\n");
            sleep (1);          //  Do some 'work'
            zmq_send (responder, "World", 5, 0);
        }
}

The service works fine until I keep the application open but when I close the application (but the service keeps running since it is a foreground service) the service stops to work (from my client application I don't see any reply to my requests using zeromq).

I tried exteding from QtService instead of Service but the app randomly crashes and the service never works (I also do not see the foreground service icon so I think that there is a problem starting a QtService as foreground service).
What I'm doing wrong? How can I obtain a working service (with the main application, which launched the service, closed) who correctly replies throught zeromq?

Thanks

[selankon]

Hi,

Maybe its too late, have you tried to run the service in a separated thread?

https://doc.qt.io/qt-5/android-services.html#service-in-separate-process