如何在sap的screen中使用ListBox

1、拖入一个编辑控件到屏幕，设置“下拉”属性为“ListBox”

2、设置Function-CODE，

3、listbox的列表的取值有三种方法：

A)默认取Dictionary；
B)使用“VRM_SET_VALUES"函数在PBO中设置 ，代码见后面代码
C)使用Process On Value-request事件和“F4IF_INT_Table_Value_request”函数设置输入帮助
其中C优于B，B优于A

代码示例：（参见SAP的样例程序，rsdemo_dropdown_list）

*屏幕事件
process before output.
  module status_0100.
   module fill_carrid.
*
process after input.
 module event_from_listbox.
 module exit at exit-command.

process on value-request.
field sflight-carrid module set_data_carrid.

 *程序
report rsdemo_dropdown_listbox .

data  init.
tables scarr.

tables spfli.
tables sflight.
tables sbook.
data  save_ok like sy-ucomm.
data  ok_code like sy-ucomm.

call screen 100.

*&---------------------------------------------------------------------*
*&      Module  STATUS_0100  OUTPUT
*&---------------------------------------------------------------------*
*       text
*----------------------------------------------------------------------*
module status_0100 output.
  if init is initial.
    set pf-status 'GRUND'.
    set titlebar '100'.

* preset of listboxes
    spfli-carrid = 'LH'.
    sflight-carrid = 'LH'.
    sbook-carrid = 'LH'.
  endif.

endmodule.                             " STATUS_0100  OUTPUT
*&---------------------------------------------------------------------*
*&      Module  SET_DATA_CARRID  INPUT
*&---------------------------------------------------------------------*
*       text
*----------------------------------------------------------------------*
module set_data_carrid input.
  types: begin of type_carrid,
         carrid like spfli-carrid,
         carrname like scarr-carrname,
         end of type_carrid.

  data itab_carrid type standard table of type_carrid with header line.

  select carrid carrname
                from scarr
                into corresponding fields of table itab_carrid.

  call function 'F4IF_INT_TABLE_VALUE_REQUEST'
       exporting
            retfield        = 'CARRID'
            value_org       = 'S'
       tables
            value_tab       = itab_carrid
       exceptions
            parameter_error = 1
            no_values_found = 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.

endmodule.                             " SET_DATA_CARRID  INPUT
*&---------------------------------------------------------------------*
*&      Module  FILL_CARRID  OUTPUT
*&---------------------------------------------------------------------*
*       text
*----------------------------------------------------------------------*
module fill_carrid output.
* Do not use this process (but it works)

  type-pools vrm.
  data values type vrm_values with header line.

  if init is initial.
    select * from scarr.
      values-text = scarr-carrname.
      values-key = scarr-carrid.
      append values.
    endselect.
    call function 'VRM_SET_VALUES'
         exporting
              id              = 'SBOOK-CARRID'
              values          = values[]
         exceptions
              id_illegal_name = 1
              others          = 2.
    if sy-subrc <> 0.
      message id sy-msgid type sy-msgty number sy-msgno
              with sy-msgv1 sy-msgv2 sy-msgv3 sy-msgv4.
    endif.

  endif.
  scarr-carrid = 'LH'.
  init = 'X'.
endmodule.                             " FILL_CARRID  OUTPUT
*&---------------------------------------------------------------------*
*&      Module  EVENT_FROM_LISTBOX  INPUT
*&---------------------------------------------------------------------*
*       text
*----------------------------------------------------------------------*
module event_from_listbox input.
  save_ok = ok_code.
  clear ok_code.
  case save_ok.
    when 'LISTBOX_2'.
      message i300(eu) with save_ok.
    when 'LISTBOX_3'.
      message i300(eu) with save_ok.
  endcase.
endmodule.                             " EVENT_FROM_LISTBOX  INPUT
*&---------------------------------------------------------------------*
*&      Module  EXIT  INPUT
*&---------------------------------------------------------------------*
*       text
*----------------------------------------------------------------------*
module exit input.
  leave program.
endmodule.                             " EXIT  INPUT