code: public void setChangeListener(OnChangeListener listener) {
          changeListener = listener;
          if (changeListener != null) {
              // add a listener to TagViewer for removed tags events
              tv.setOnRemovedTagListener(new TagsViewer.OnRemovedListener() {
                  @Override
                  public void onRemovedTag(String tag) {
                      notifyChangeListener();
                  }
              });
          }
      }
docs: Set the change listener.
  
  @param listener