How to read the ALV list saved layout metadata?

I have an ALV list as an output of the program and need to be able to dynamically get / fetch the columns and their positions.

The users can also save the columns / positions as a layout for future use and I want to get this information for the saved layouts.

I am expecting to get the columns and their positions of an ALV list as an internal table, to use it further, for example, to generate .xls file.

Solution

You can achieve it in the way described below. I wrote a sample code snippet with comments. Basically the starting table is LTDX.

First read the layouts for the program using FM LT_VARIANTS_READ_FROM_LTDX. Replace REPORT_NAME_REPLACE with your program name of interest. Additionally you can filter layouts for specific user(s) - uncomment lines with range table lt_r_uname and replace LOGIN_REPLACE with your login.

TYPES: ty_r_repid TYPE RANGE OF syrepid,
       ty_r_uname TYPE RANGE OF syst_uname.

DATA: lt_variants TYPE TABLE OF ltvariant.

DATA(lt_r_repid) = VALUE ty_r_repid(
  ( sign = 'I' option = 'EQ' low = 'REPORT_NAME_REPLACE' )
).
DATA(lt_r_uname) = VALUE ty_r_uname(
  ( sign = 'I' option = 'EQ' low = 'LOGIN_REPLACE' )
).

CALL FUNCTION 'LT_VARIANTS_READ_FROM_LTDX'
  EXPORTING
    i_tool       = 'LT'
    i_text       = 'X'
  TABLES
    et_variants  = lt_variants
    it_ra_report = lt_r_repid.
*      it_ra_username = lt_r_uname.

IF sy-subrc <> 0.
  WRITE: / 'Not layout(s) found.'.
  EXIT.
ENDIF.

Next for the found layout(s) read the data - basic field catalog - with FM LT_DBDATA_READ_FROM_LTDX and afterwards the field catalog itself with FM LT_FC_LOAD.

LOOP AT lt_variants ASSIGNING FIELD-SYMBOL(<fs_variant>).
  DATA: lt_fcat_base TYPE TABLE OF ltdxdata,
        lt_fcat_def  TYPE kkblo_t_fieldcat,
        lt_fcat      TYPE kkblo_t_fieldcat,
        ls_layout    TYPE kkblo_layout.

  DATA(ls_key_base) = CORRESPONDING ltdxkey( <fs_variant> ).
  CALL FUNCTION 'LT_DBDATA_READ_FROM_LTDX'
    EXPORTING
      i_tool       = 'LT'
      is_varkey    = ls_key_base
    TABLES
      t_dbfieldcat = lt_fcat_base.

  IF sy-subrc = 0.
    DATA(ls_key) = CORRESPONDING disvariant( <fs_variant> ).
    LOOP AT lt_fcat_base ASSIGNING FIELD-SYMBOL(<fs_fcat_base>).
      COLLECT VALUE kkblo_fieldcat( fieldname = <fs_fcat_base>-key1 )
              INTO lt_fcat_def.
    ENDLOOP.

    CALL FUNCTION 'LT_FC_LOAD'
      EXPORTING
        is_variant          = ls_key
        i_tabname           = '1'
      IMPORTING
        et_fieldcat         = lt_fcat
      CHANGING
        cs_layout           = ls_layout
        ct_default_fieldcat = lt_fcat_def.

    IF sy-subrc = 0.
      LOOP AT lt_fcat_base ASSIGNING <fs_fcat_base>
        WHERE param = 'NO_OUT' AND value = 'X'.

        DELETE lt_fcat WHERE fieldname = <fs_fcat_base>-key1.
      ENDLOOP.

      SORT lt_fcat BY col_pos.

*     Field catalog for layout is in internal table lt_fcat
*     Debug output: layout and fields

      WRITE: / |Layout: { <fs_variant>-variant } [{ <fs_variant>-username }] |.
      LOOP AT lt_fcat ASSIGNING FIELD-SYMBOL(<ls_fcat>).
        WRITE: /9 |{ <ls_fcat>-fieldname }|.
      ENDLOOP.

    ELSE.
      WRITE: |No field catalog found for layout { <fs_variant>-variant }|.
    ENDIF.

    CLEAR: lt_fcat_def.
  ELSE.
    WRITE: |No data found for layout { <fs_variant>-variant }|.
  ENDIF.
ENDLOOP.

The internal table lt_fcat contains columns of the layout: component fieldname the name of the column and col_pos its position. I filtered out from the internal table the columns which have parameter NO_OUT = 'X' and therefore are not displayed in the layout.