android - onLocationChanged never called

Question

I am currently implementing a feature of getting user's current location with Google API.

@Override
public void onLocationChanged(Location location) {
    mLastLocation = location;
    LatLng latLng = new LatLng(location.getLatitude(), location.getLongitude());
    mMap.moveCamera(CameraUpdateFactory.newLatLng(latLng)); // user location center in map (every update)
    mMap.animateCamera(CameraUpdateFactory.zoomTo(11));
}

@Override
public void onConnected(@Nullable Bundle bundle) {
    if (ActivityCompat.checkSelfPermission(this, android.Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this, android.Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
    }
    Location location = LocationServices.FusedLocationApi.getLastLocation(mGoogleApiClient);
    if (location == null) {
        mLocationRequest = LocationRequest.create()
                .setPriority(LocationRequest.PRIORITY_HIGH_ACCURACY)
                .setSmallestDisplacement(DISPLACEMENT)
                .setInterval(UPDATE_INTERVAL)
                .setFastestInterval(FASTEST_INTERVAL);
        LocationServices.FusedLocationApi.requestLocationUpdates(mGoogleApiClient, mLocationRequest, this);
    }else{

    }
}

However, onLocationChanged callback function is never triggered when I requestLocationUpdates in onConnected. I have log several status out, showing that mLocationRequest is created and requestLocationUpdates is called.

Any ideas on this? Thank you all!