code: public void addScrollListener(@NonNull final ScrollListener listener) {
          Condition.INSTANCE.ensureNotNull(listener, "The listener may not be null");
          this.scrollListeners.add(listener);
      }
docs: Adds a listener, which should be notified, when the scroll view is scrolled.
  
  @param listener
  The listener, which should be added, as an instance of the type {@link
  ScrollListener}. The listener may not be null