code: public File getBackTop() {
          if (getArguments().containsKey(KEY_START_PATH)) {
              String keyStartPath = getArguments().getString(KEY_START_PATH);
  
              if (keyStartPath == null)
                  return new File("/");
  
              return getPath(keyStartPath);
          } else {
              return new File("/");
          }
      }
docs: For consistency, the top level the back button checks against should be the start path.
  But it will fall back on /.