Dropdown in FPM_FORM_UIBB

Hello everybody,

I'm trying to add an DropDown programtically to a FormUIBB.

Here is what I'm doing:

In Get_Default_config:

1. io_layout_config->add_group

2. ls_action-event_id = 'ON_DROP_LAYOUTS'.

    APPEND ls_action TO lt_actions.

3.

CALL METHOD io_layout_config->add_element

        EXPORTING

          iv_group_id         = lv_group_id

          iv_name             = 'LAYOUTS' "lv_name

          iv_display_type     = 'DD'

          iv_visibility_label = '02'

          it_element_action   = lt_actions

        RECEIVING

          rv_element_id       = lv_el_id.

And in Get_Data:

1. "LT_LAYOUT_MAIN is correctly filled via a Select.

LOOP AT LT_LAYOUT_MAIN INTO LS_LAYOUT_MAIN.

      ls_value-value = LS_LAYOUT_MAIN-LAYOUT_KEY.

      ls_value-text = LS_LAYOUT_MAIN-DESCRIPTION.

      APPEND ls_value TO lt_values.

ENDLOOP.

    ls_field_usage-fixed_values = lt_values.

    ls_field_usage-fixed_values_changed = abap_true.

    ls_field_usage-enabled = abap_true.

    ls_field_usage-visibility = '02'.

    APPEND ls_field_usage TO ct_field_usage.

    CLEAR: ls_value, lt_values.

Then I create a configuration with the feeder-class in FLUID. But if I open the configuration of the UIBB in fluid it gives me following error:

"Anzeigeart DD ist hier nicht erlaubt" roughly translated: "Displaytype DD is not allowed here".

Am I missing something?

Thank you in advance!