code: @SuppressWarnings({"WeakerAccess", "unused"})
     public Set<String> getViewList()
     {
        if (this.rootElement == null)
           throw new IllegalArgumentException("SVG document is empty");
  
        List<SvgObject>  viewElems = getElementsByTagName(View.NODE_NAME);
  
        Set<String>  viewIds = new HashSet<>(viewElems.size());
        for (SvgObject elem: viewElems)
        {
           View  view = (View) elem;
           if (view.id != null)
              viewIds.add(view.id);
           else
              Log.w("AndroidSVG", "getViewList(): found a <view> without an id attribute");
        }
        return viewIds;
     }
docs: Returns a list of ids for all {@code <view>} elements in this SVG document.
  <p>
  The returned view ids could be used when calling and of the {@code renderViewToX()} methods.
  
  @return the list of id strings.
  @throws IllegalArgumentException if there is no current SVG document loaded.