code: public void downloadTiles(OfflineTiles offlineTiles, RouteTileDownloadListener listener) {
      new RouteTileDownloader(offlineNavigator, tilePath, listener).startDownload(offlineTiles);
    }
docs: Starts the download of tiles specified by the provided {@link OfflineTiles} object.
  
  @param offlineTiles object specifying parameters for the tile request
  @param listener     which is updated on error, on progress update and on completion