How to load offline map tiles from custom location

I have my offline map tiles on the android device here, they are already unzipped:

/sdcard/application-name/uuid/tiles

and I have set the OSM cache like so:

File applicationDir = new File(Environment.getExternalStorageDirectory(), File.separator + "application-name" + File.separator + "uuid" + File.separator);
OpenStreetMapTileProviderConstants.setCachePath(applicationDir.getAbsolutePath());

I then set up the TileSource:

ITileSource tileSource = new XYTileSource ("tiles", 0, 18, 256, ".png", new String[0]);

and the TileProvider:

tileProvider = new MapTileProviderBasic(getActivity());
tileProvider.setTileSource(tileSource);

I have set

OpenStreetMapTileProviderConstants.DEBUGMODE = true;

and I get a load of Tile doesn't exist messages.

Any suggestions gratefully received! Thanks.