fusedLocationProviderClient.lastLocation.addOnSuccessListener always null

You can use getLocationAvailability() method on your FusedLocationPrivedClient object and if it returns true then only use getLastLocation() method otherwise use requestLocationUpdates() method like this :

FusedLocationProviderClient fusedLocationProviderClient =
            LocationServices.getFusedLocationProviderClient(InitActivity.this);
    if (ActivityCompat.checkSelfPermission(this.getApplicationContext(),
            android.Manifest.permission.ACCESS_FINE_LOCATION)
            == PackageManager.PERMISSION_GRANTED) {

fusedLocationProviderClient.getLocationAvailability().addOnSuccessListener(new OnSuccessListener<LocationAvailability>() {
                @Override
                public void onSuccess(LocationAvailability locationAvailability) {
                    Log.d(TAG, "onSuccess: locationAvailability.isLocationAvailable " + locationAvailability.isLocationAvailable());
                    if (locationAvailability.isLocationAvailable()) {
                        if (ActivityCompat.checkSelfPermission(InitActivity.this.getApplicationContext(),
                                android.Manifest.permission.ACCESS_FINE_LOCATION)
                                == PackageManager.PERMISSION_GRANTED) {
                            Task<Location> locationTask = fusedLocationProviderClient.getLastLocation();
                            locationTask.addOnCompleteListener(new OnCompleteListener<Location>() {
                                @Override
                                public void onComplete(@NonNull Task<Location> task) {
                                    Location location = task.getResult();                                    
                                }
                            });
                        } else {
                            requestLocationPermissions ();
                        }

                    } else {
fusedLocationProviderClient.requestLocationUpdates(locationRequest, pendingIntent);

                    }

                }
            });
        } else {
            requestLocationPermissions ();
        }

I found a solution, this is what happens, when the location is null it means the location cache was cleared, this happens when turning off GPS, so when I was turning it on there was no last location to get, what I did was this:

checkLocationSettings(callingActivity, turnOnGpsRequestCode, callback) {
                // Location settings successful
                mFusedLocationProviderClient!!.lastLocation
                        .addOnSuccessListener(callingActivity) {
                            location ->
                            if (location == null || location.accuracy > 100) {
                                mLocationCallback = object : LocationCallback() {
                                    override fun onLocationResult(locationResult: LocationResult?) {
                                        stopLocationUpdates()
                                        if (locationResult != null && locationResult.locations.isNotEmpty()) {
                                            val newLocation = locationResult.locations[0]
                                            callback.onCallback(Status.SUCCESS, newLocation)
                                        } else {
                                            callback.onCallback(Status.ERROR_LOCATION, null)
                                        }
                                    }
                                }

                                mFusedLocationProviderClient!!.requestLocationUpdates(getLocationRequest(),
                                        mLocationCallback, null)
                            } else {
                                callback.onCallback(Status.SUCCESS, location)
                            }
                        }
                        .addOnFailureListener {
                            callback.onCallback(Status.ERROR_UNKNOWN, null)
                        }
            }

When the location is null, start requesting locations using a callback and

mFusedLocationProviderClient!!.requestLocationUpdates(getLocationRequest(), mLocationCallback, null)

Then when the callback is called, a new location is got and it starts getting location again.

Sometimes it happens that when you turn on the GPS, the location is not null but the accuracy is bad, so I also check if location accuracy is good enough (For me good enough is 100 meters)