Set selection-screen text when the program first run

*&---------------------------------------------------------------------*
*& Report  ZBOB_INIT_SL_TXT
*&
*&---------------------------------------------------------------------*
*& Desc: Init selection screen without set text-element
*& Author: 翱翔云天
*& Website: www.abaptech.com
*&---------------------------------------------------------------------*
 
REPORT  ZBOB_INIT_SL_TXT.
 
TABLES: EKKO.
 
* Text object
data: it_txt TYPE STANDARD TABLE OF textpool,
      wa_txt LIKE LINE OF it_txt.
* First time or not indicator
data: txt_flag.
 
* Define selection field
SELECT-OPTIONS: s_ebeln for ekko-ebeln.
 
INITIALIZATION.
* Get selection text
  read TEXTPOOL sy-cprog into it_txt LANGUAGE sy-langu.
* Delete empty entry
  delete it_txt where entry = space and id = 'S'.
  read table it_txt into wa_txt with key key = 'O_IND'.
  if not wa_txt-entry = '        First time'.
*   First time run program, add selection text
    wa_txt-id = 'S'. wa_txt-key = 'S_EBELN'.
    wa_txt-entry = '        Purchase Order'.
    APPEND wa_txt TO it_txt.
 
    wa_txt-id = 'S'. wa_txt-key = 'O_IND'.
    wa_txt-entry = '        First time'.
    APPEND wa_txt TO it_txt.
    INSERT TEXTPOOL sy-cprog FROM it_txt LANGUAGE sy-langu.
    txt_flag = 'X'.
 
    MESSAGE i888(sabapdocu) WITH
     'This is the first time you start this report.'
    'After the next start the '
     'selectiontexts are initialized!'.
  endif.
 
start-of-SELECTION.
  IF txt_flag = 'X'.
*    Information message
    MESSAGE i888(sabapdocu) WITH
     'Restart of Report!'
     'Tis happens only at the first start'.
    SET  SCREEN 0.
    STOP.
  ENDIF.