Issue loading previously created tiles from MapquestOSM folder

I have create a simple OSM Map application for offline viewing and navigation. While creating the app, I followed the following tutorials:

http://mobiledevstories.wordpress.com/page/2/
http://www.haakseth.com/?p=30
The application is working fine when Internet connectivity is working. But, when there is not internet connection, the app should load tiles from the /sdcard/osmdroid/ folder which is not happening. No tiles are getting loaded when I am offline.

My main intention is to allow the users to download tiles of different cities from the internet and use them later when they do not have internet connectivity.

The activity which I have created:

public class MainActivity extends Activity {

    double myCurrentLatitude;
    double myCurrentLongitude;

    // The MapView variable:
    MapView mapView;

    List<Overlay> mapOverlays;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        // get current location
        GPSTracker tracker = new GPSTracker(this);
        if (tracker.canGetLocation() == false) {
            tracker.showSettingsAlert();
        } else {
            myCurrentLatitude = tracker.getLatitude();
            myCurrentLongitude = tracker.getLongitude();
        }

        mapView = (MapView) findViewById(R.id.mapview);
        mapView.setClickable(true);
        // mapView.setBuiltInZoomControls(true);
        // for only pinch zoom
        mapView.setMultiTouchControls(true);
        mapView.setTileSource(TileSourceFactory.MAPQUESTOSM);
        mapView.getController().setZoom(15);
        mapView.getController().setCenter(
                new GeoPoint(myCurrentLatitude, myCurrentLongitude));

//      mapView.getController().setCenter(
//              new GeoPoint(18.9750, 72.8258));

        mapOverlays = mapView.getOverlays();

        showMyCurrentLocation();
        showFoodJoint("1",22.5850, 88.3750, "Test food", "Maniktala");
        showFoodJoint("2",22.576600900000000000, 88.367032500000050000, "Test food 2", "College Street");


        // =====For showing restaurant location on
        // map======================//

    }

    // =====For showing my current location on map======================//
    public void showMyCurrentLocation() {
        Drawable myLocationDrawable = this.getResources().getDrawable(
                R.drawable.pin_for_my_location);

        MapItemizedOverlay itemizedoverlayForMyLocation = new MapItemizedOverlay(
                myLocationDrawable, this);
        itemizedoverlayForMyLocation.setEnabled(true);

        itemizedoverlayForMyLocation.setEnabled(true);

        // setting pin to my current position on the map

        GeoPoint myCurrentPoint = new GeoPoint(myCurrentLatitude,
                myCurrentLongitude);
//      GeoPoint myCurrentPoint = new GeoPoint(18.9750,
//              72.8258);
        OverlayItem overlayitem = new OverlayItem("Id","Hello", "You are here",
                myCurrentPoint);

        itemizedoverlayForMyLocation.addOverlay(overlayitem);

        mapOverlays.add(itemizedoverlayForMyLocation);

        mapView.getController().setZoom(15);
        mapView.getController().setCenter(myCurrentPoint);
    }

    // =====For showing my current location on map======================//


    // =====For showing restaurant location======================//
    public void showFoodJoint(String foodJointId,double foodJointLat, double foodJointLon, String foodJointName, String foodJointDescription)
    {
        Drawable restaurantLocationDrawable = this.getResources().getDrawable(
                R.drawable.pin_for_restaurant_location);
        MapItemizedOverlay itemizedoverlayForRestaurant = new MapItemizedOverlay(
                restaurantLocationDrawable, this);

        GeoPoint myPoint1 = new GeoPoint(foodJointLat, foodJointLon);
        OverlayItem overlayitem2 = new OverlayItem(foodJointId,foodJointName,foodJointDescription, myPoint1);

        itemizedoverlayForRestaurant.addOverlay(overlayitem2);

        mapOverlays.add(itemizedoverlayForRestaurant);
    }

    // =====For showing restaurant location======================//


    // For routing

    // ======================================================================================================
    /**
     * Add a route overlay between two geopoints with Bubble overlays on the
     * route points.
     * 
     * @param startPoint
     *            Route start.
     * @param endPoint
     *            Route end.
     */
    // ======================================================================================================
    public void addRouteOverlay(GeoPoint startPoint, GeoPoint endPoint) {
        // road manager
        RoadManager roadManager = new OSRMRoadManager();

        // start and end points
        ArrayList<GeoPoint> waypoints = new ArrayList<GeoPoint>();
        waypoints.add(startPoint);
        // GeoPoint endPoint = new GeoPoint(48.4, -1.9);
        waypoints.add(endPoint);
        // roadManager.addRequestOption("routeType=bicycle");
        // retreive the road between those points
        Road road = roadManager.getRoad(waypoints);
        // Polyline with the route shape
        org.osmdroid.bonuspack.overlays.Polyline roadOverlay = RoadManager
                .buildRoadOverlay(road, this);
        // Polyline to the overlays of your map
        mapView.getOverlays().add(roadOverlay);
        // Refresh the map
        mapView.invalidate();

    }// ===================================================================================================

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

public void makeAToast(String str) {
        Toast toast = Toast.makeText(this, str, Toast.LENGTH_LONG);
        toast.setGravity(Gravity.CENTER, 0, 0);
        toast.show();
    }

}

Where am I going wrong?

double cross-post !!!

what can I do?