Geofencing in background on Android 8 or 9 does not work

I try to make appear a push alert to the user when he reach a defined zone.

So I coded my app from : https://developer.android.com/training/location/geofencing

It is working perfectly if my app is running with a service following the location of the user.

It also work if I start google map for example, that will track my location too. Pushes will appear.

But if I close my app the push won't appear, so the geofencing is not detected if no app is tracking my location.

Is it normal ? How to make it work always ? What is the point of geofencing if you need a foreground service following your location ?

 public void createGeofenceAlerts(LatLng latLng, int radius) {
    final Geofence enter = buildGeofence(ID_ENTER, latLng, radius, Geofence.GEOFENCE_TRANSITION_ENTER);
    final Geofence exit = buildGeofence(ID_EXIT, latLng, radius, Geofence.GEOFENCE_TRANSITION_EXIT);
    final Geofence dwell = buildGeofence(ID_DWELL, latLng, radius, Geofence.GEOFENCE_TRANSITION_DWELL);

    GeofencingRequest request = new GeofencingRequest.Builder()
            .setInitialTrigger(GeofencingRequest.INITIAL_TRIGGER_ENTER)
            .addGeofence(enter)
            .addGeofence(exit)
            .addGeofence(dwell)
            .build();

    fencingClient.addGeofences(request, getGeofencePendingIntent()).addOnSuccessListener(new OnSuccessListener<Void>() {
        @Override
        public void onSuccess(Void aVoid) {
            Timber.i("succes");
            Toast.makeText(mContext, "Geofence added", Toast.LENGTH_LONG).show();
        }
    }).addOnFailureListener(new OnFailureListener() {
        @Override
        public void onFailure(@NonNull Exception e) {
            Timber.e(e,"failure");
            Toast.makeText(mContext, "Geofence ERROR", Toast.LENGTH_LONG).show();
        }
    });
}

private PendingIntent getGeofencePendingIntent() {
    Intent intent = new Intent(mContext, GeofenceTransitionsIntentService.class);
    PendingIntent pending = PendingIntent.getService(
            mContext,
            0,
            intent,
            PendingIntent.FLAG_UPDATE_CURRENT);
    return pending;
}

private Geofence buildGeofence(String id, LatLng center, int radius, int transitionType) {
    Geofence.Builder builder = new Geofence.Builder()
            // 1
            .setRequestId(id)
            // 2
            .setCircularRegion(
                    center.getLatitude(),
                    center.getLongitude(),
                    radius)
            // 3
            .setTransitionTypes(transitionType)
            // 4
            .setExpirationDuration(Geofence.NEVER_EXPIRE);
    if (transitionType == Geofence.GEOFENCE_TRANSITION_DWELL) {
        builder.setLoiteringDelay(LOITERING_DELAY);
    }

    return builder.build();
}

I think I found a solution, tested on Android 9. I used the Google documentation https://developer.android.com/training/location/geofencing but I replaced the service by a broadcast receiver.

My GeofenceManager :

private val braodcastPendingIntent: PendingIntent
    get() {
        val intent = Intent(mContext, GeofenceTransitionsBroadcastReceiver::class.java)
        val pending = PendingIntent.getBroadcast(
                mContext.applicationContext,
                0,
                intent,
                PendingIntent.FLAG_UPDATE_CURRENT)
        return pending
    }

 fun createGeofenceAlerts(latLng: LatLng, radiusMeter: Int, isBroadcast: Boolean) {
    val enter = buildGeofence(ID_ENTER, latLng, radiusMeter, Geofence.GEOFENCE_TRANSITION_ENTER)
    val exit = buildGeofence(ID_EXIT, latLng, radiusMeter, Geofence.GEOFENCE_TRANSITION_EXIT)
    val dwell = buildGeofence(ID_DWELL, latLng, radiusMeter, Geofence.GEOFENCE_TRANSITION_DWELL)

    val request = GeofencingRequest.Builder()
            .setInitialTrigger(GeofencingRequest.INITIAL_TRIGGER_ENTER)
            .addGeofence(enter)
            .addGeofence(exit)
            .addGeofence(dwell)
            .build()

    val pending = if (isBroadcast) {
        braodcastPendingIntent
    } else {
        servicePendingIntent
    }
    fencingClient.addGeofences(request, pending).addOnSuccessListener {
        Timber.i("succes")
        Toast.makeText(mContext, "Geofence added", Toast.LENGTH_LONG).show()
    }.addOnFailureListener { e ->
        Timber.e(e, "failure")
        Toast.makeText(mContext, "Geofence ERROR", Toast.LENGTH_LONG).show()
    }
}

private fun buildGeofence(id: String, center: LatLng, radius: Int, transitionType: Int): Geofence {
    val builder = Geofence.Builder()
            // 1
            .setRequestId(id)
            // 2
            .setCircularRegion(
                    center.latitude,
                    center.longitude,
                    radius.toFloat())
            // 3
            .setTransitionTypes(transitionType)
            // 4
            .setExpirationDuration(Geofence.NEVER_EXPIRE)
    if (transitionType == Geofence.GEOFENCE_TRANSITION_DWELL) {
        builder.setLoiteringDelay(LOITERING_DELAY)
    }

    return builder.build()
}

My BroadcastReceiver, obviously you need to declare it in the manfifest :

class GeofenceTransitionsBroadcastReceiver : BroadcastReceiver() {
override fun onReceive(context: Context, intent: Intent) {
    Timber.i("received")
    val geofencingEvent = GeofencingEvent.fromIntent(intent)
    if (geofencingEvent.hasError()) {
        Timber.e("Geofence error")
        return
    }

    // Get the transition type.
    val geofenceTransition = geofencingEvent.geofenceTransition

    // Test that the reported transition was of interest.
    if (geofenceTransition == Geofence.GEOFENCE_TRANSITION_ENTER || geofenceTransition == Geofence.GEOFENCE_TRANSITION_EXIT
            || geofenceTransition == Geofence.GEOFENCE_TRANSITION_DWELL) {

        // Get the geofences that were triggered. A single event can trigger
        // multiple geofences.
        val triggeringGeofences = geofencingEvent.triggeringGeofences

        // Get the transition details as a String.
        val geofenceTransitionDetails = GeofenceManager.getGeofenceTransitionDetails(
                geofenceTransition,
                triggeringGeofences, true
        )

        // Send notification and log the transition details.
        GeofenceManager.sendNotification(context, geofenceTransition, geofenceTransitionDetails)
        Timber.i(geofenceTransitionDetails)
    } else {
        // Log the error.
        Timber.e("Unknown geo event : %d", geofenceTransition)
    }
}

The important part is to know that on Android 8 and 9 the geofencing has a latency of 2 minutes.