docs: public static long updateStoragePrefreneces(Context ctx){
  
          //loads the osmdroid config from the shared preferences object.
          //if this is the first time launching this app, all settings are set defaults with one exception,
          //the tile cache. the default is the largest write storage partition, which could end up being
          //this app's private storage, depending on device config and permissions
  
          Configuration.getInstance().load(ctx, PreferenceManager.getDefaultSharedPreferences(ctx));
  
          //also note that our preference activity has the corresponding save method on the config object, but it can be called at any time.
  
  
          File dbFile = new File(Configuration.getInstance().getOsmdroidTileCache().getAbsolutePath() + File.separator + SqlTileWriter.DATABASE_FILENAME);
          if (dbFile.exists()) {
              return dbFile.length();
          }
          return -1;
      }