code: @Nullable
      public Object onActionPressed() {
          View existingForm = getChildAt(getChildCount() == 1 ? 0 : 2);
          if (existingForm != null) {
              FormView form = (FormView) existingForm;
              return form.submitForm();
          }
          return null;
      }
docs: ActionButton has been clicked, and validation should be run on the current
  visible form. If this validation passes, an action event will be returned.
  
  @return the action event of the current visible form or null if validation failed