ALV_LIST_DISPLAY default layout problem

Question

hi every body
I am trying to display my itab content using FM ALV_LIST_DISPLAY 
the problem facing is
in my internal table there r 100 fields if i create field catalog for all fields
are displaying in ALV list
my requirement is out of 100 fields only 20 fields need to be displayed
every time we run the report and who ever runs the report
and also there should be a provision to the user to select specific fields
in specific order from the available 100 fields in the internal table.
please suggest me how to solve this one
Thanks in advance for your kind suggestions

Answer 1

Build the filed catalog using FM  'REUSE_ALV_FIELDCATALOG_MERGE'.
Loop thru the fld catalog and hide the unnecc ones. Users can create variants
in the ALV and provide provide a field on the screen to select a variant .
Kindly Go thru cod below :
FORM set_alv_fieldcat_n_layout
     CHANGING c_layout       TYPE  slis_layout_alv
              c_tab_fieldcat TYPE  slis_t_fieldcat_alv.
  FIELD-SYMBOLS: <wa_fieldcat> TYPE slis_fieldcat_alv.
  DATA : l_pos TYPE i VALUE 4.
create default field catalogue with DDIC information of
output structure:
  CALL FUNCTION 'REUSE_ALV_FIELDCATALOG_MERGE'
    EXPORTING
    i_program_name               = g_con_callback_prog
    i_internal_tabname           = 'GT_OUTTAB'
     i_structure_name             = 'FTI_INT_INSTR_DATA'
    i_client_never_display       = 'X'
    i_inclname                   = sy-repid
   I_BYPASSING_BUFFER           =
   I_BUFFER_ACTIVE              =
    CHANGING
      ct_fieldcat                  = c_tab_fieldcat
    EXCEPTIONS
      inconsistent_interface       = 1
      program_error                = 2
      OTHERS                       = 3.
  IF sy-subrc <> 0.
    MESSAGE ID sy-msgid TYPE sy-msgty NUMBER sy-msgno
            WITH sy-msgv1 sy-msgv2 sy-msgv3 sy-msgv4.
  ENDIF.
modify the field catalogue in a specific required way:
  LOOP AT c_tab_fieldcat ASSIGNING <wa_fieldcat>.
    IF <wa_fieldcat>-fieldname = 'MANDT'.
      DELETE c_tab_fieldcat.
      CONTINUE.
    ENDIF.
    IF <wa_fieldcat>-fieldname = g_param1.
      <wa_fieldcat>-col_pos = '3'.
    ELSEIF <wa_fieldcat>-fieldname = g_param2.
      <wa_fieldcat>-col_pos = '4'.
    ELSEIF <wa_fieldcat>-fieldname EQ 'ACTIVE_PASSIVE'.
      <wa_fieldcat>-col_pos = '2'.
    ELSEIF <wa_fieldcat>-fieldname EQ 'ICON_SUBTOTAL'.
      <wa_fieldcat>-col_pos = '1'.
    ELSE.
      <wa_fieldcat>-col_pos = l_pos.
      l_pos = l_pos + 1.
    ENDIF.
    IF <wa_fieldcat>-fieldname = g_param1 OR
       <wa_fieldcat>-fieldname = g_param2 OR
       <wa_fieldcat>-fieldname = 'ACTIVE_PASSIVE' OR
       <wa_fieldcat>-fieldname CP '*_LC' OR
       <wa_fieldcat>-fieldname CP '*_PC' OR
       <wa_fieldcat>-fieldname CP '*_DC' OR
       <wa_fieldcat>-fieldname CP 'MED_*' OR
       <wa_fieldcat>-fieldname CP 'ICON_*'.
    ELSE.
      <wa_fieldcat>-no_out = 'X'.
    ENDIF.
    IF p_skflg = ftico_xtrue.
      IF <wa_fieldcat>-fieldname CP '*_LC' OR
         <wa_fieldcat>-fieldname CP '*_PC' OR
         <wa_fieldcat>-fieldname CP '*_DC'.
        <wa_fieldcat>-round = p_skalv.
        <wa_fieldcat>-decimals_out = p_decim.
      ENDIF.
    ENDIF.
    IF <wa_fieldcat>-fieldname CP '*_LC' OR
       <wa_fieldcat>-fieldname CP '*_PC' OR
       <wa_fieldcat>-fieldname CP '*_DC'.
    ELSE.
      <wa_fieldcat>-key_sel = 'X'.
      <wa_fieldcat>-no_sum = 'X'.
    ENDIF.
    IF <wa_fieldcat>-fieldname CP '*_LC' OR
       <wa_fieldcat>-fieldname CP '*_PC' OR
       <wa_fieldcat>-fieldname CP '*_DC'.
      <wa_fieldcat>-outputlen = '16'.
    ENDIF.
    IF <wa_fieldcat>-fieldname EQ 'ANZGW' OR
       <wa_fieldcat>-fieldname EQ 'CALC_CCY' OR
       <wa_fieldcat>-fieldname EQ 'NPV_CC' OR
       <wa_fieldcat>-fieldname EQ 'CLEAN_PRICE_CC' OR
       <wa_fieldcat>-fieldname CP 'ERR_*'.
      DELETE c_tab_fieldcat.
      CONTINUE.
     <wa_fieldcat>-no_out = 'X'.
    ENDIF.
    IF <wa_fieldcat>-fieldname EQ 'INT_CAT' OR
       <wa_fieldcat>-fieldname EQ 'ACTIVE_PASSIVE'.
      <wa_fieldcat>-outputlen = '3'.
    ENDIF.
    IF <wa_fieldcat>-fieldname CP 'ICON_*'.
      <wa_fieldcat>-icon = 'X'.
      <wa_fieldcat>-outputlen = 3.
    ENDIF.
    IF <wa_fieldcat>-fieldname EQ g_param1 OR
       <wa_fieldcat>-fieldname EQ g_param2 OR
       <wa_fieldcat>-fieldname EQ 'ACTIVE_PASSIVE'.
      <wa_fieldcat>-key = 'X'.
    ENDIF.
  ENDLOOP.
ENDFORM.                    " set_alv_fieldcat_n_layout