FusedLocationProviderClient onLocationResult never called

Question

I 'm trying to get location of user every time user open my app , here is my code. I notice that onLocationResult method is never called and i can't get the location update. Can anyone help me solve this ?

    final LocationRequest mLocationRequest = new LocationRequest();
    mLocationRequest.setInterval(10000);
    mLocationRequest.setFastestInterval(5000);
    mLocationRequest.setPriority(LocationRequest.PRIORITY_LOW_POWER);

    LocationSettingsRequest.Builder builder = new LocationSettingsRequest.Builder()
            .addLocationRequest(mLocationRequest);

    SettingsClient client = LocationServices.getSettingsClient(this);
    Task<LocationSettingsResponse> task = client.checkLocationSettings(builder.build());

    task.addOnSuccessListener(this, new OnSuccessListener<LocationSettingsResponse>() {
        @Override
        public void onSuccess(LocationSettingsResponse locationSettingsResponse) {
            // All location settings are satisfied. The client can initialize
            // location requests here.
            // ...
            LocationCallback mLocationCallback = new LocationCallback() {
                @Override
                public void onLocationResult(LocationResult locationResult) {
                    if (locationResult == null) {
                        return;
                    }
                    for (Location location : locationResult.getLocations()) {
                        Log.d("asdffff",""+ location.getLatitude());
                        Log.d("asdffff",""+ location.getLongitude());
                    }
                };
            };
            mFusedLocationProviderClient.requestLocationUpdates(mLocationRequest,
                    mLocationCallback,
                    null /* Looper */);
        }
    });