code: public void addPositionUpdateListener(@NonNull PositionUpdateListener listener) {
          listeners.add(listener);
          if (isReady()) {
              getToView().getPositionAnimator().addPositionUpdateListener(listener);
          }
      }
docs: Adds position state changes listener that will be notified during animations.
  
  @param listener Position listener
  @see ViewPositionAnimator#addPositionUpdateListener(PositionUpdateListener)