code: public void add(final View view, final ViewGroup parent, int index) {
          if (view.getParent() == null) {
              view.setAlpha(0);
              parent.addView(view, index);
              if (durationSet) {
                  view.animate().setDuration(duration);
              }
              view.animate().alpha(1);
          }
      }
docs: Adds a view to the specified parent at the specified index in the parent's
  child list and then fades in the view. The view must
  not currently be parented - if its parent is not null, the method returns without
  doing anything.
  
  @param view   The view to be added
  @param parent The parent to which the view is added
  @param index  The index at which the view is added in the parent's child list