code: private void cleanup() {
  		for (Rectangle rectangle : labelBgs) {
  			mapWidget.render(rectangle, RenderGroup.SCREEN, RenderStatus.DELETE);
  		}
  		labelBgs.clear();
  
  		for (Text text : labelTxts) {
  			mapWidget.render(text, RenderGroup.SCREEN, RenderStatus.DELETE);
  		}
  		labelTxts.clear();
  
  		centroids.clear();
  	}
docs: ------------------------------------------------------------------------