docs: private void showMarker(FolderOverlay newMarker) {
          boolean modified = false;
          if (this.mCurrentBackgroundContentFolder != null) {
              Log.d(TAG,"showMarker remove old " + this.mCurrentBackgroundContentFolder.getItems().size());
              this.mMapView.getOverlays().remove(this.mCurrentBackgroundContentFolder);
              this.mCurrentBackgroundContentFolder.onDetach(mMapView);
              this.mCurrentBackgroundContentFolder = null;
              modified = true;
          }
  
          if (newMarker != null) {
              this.mCurrentBackgroundContentFolder = newMarker;
              Log.d(TAG,"showMarker add new " + this.mCurrentBackgroundContentFolder.getItems().size() + ", isAnimating=" + mMapView.isAnimating());
              mMapView.getOverlays().add(newMarker);
              modified = true;
          }
  
          if (modified) {
              if (mMapView.isAnimating()) {
                  mMapView.postInvalidate();
              } else {
                  mMapView.invalidate();
              }
          }
  		
      }