在AT SELECTION-SCREEN ON VALUE-REQUEST事件中，是不能直接取得选择屏幕字段的默认值或输入的值，而是需要通过函数 DYNP_VALUES_READ读取。

例子程序：

 

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REPORT ZTEST_F4_DEFAULT.   PARAMETERS: p_folder TYPE file_table-filename.     INITIALIZATION.   * 初始化 p_folder = 'C:\ZPKF'.   *&---------------------------------------------------------------------* *&   Event AT SELECTION-SCREEN *&---------------------------------------------------------------------* AT SELECTION-SCREEN ON VALUE-REQUEST FOR p_folder.   PERFORM frm_f4_pfolder.   *&---------------------------------------------------------------------* *&      Form  FRM_F4_PFOLDER *&---------------------------------------------------------------------* *       text *----------------------------------------------------------------------* *  -->  p1        text *  <--  p2        text *----------------------------------------------------------------------* FORM frm_f4_pfolder .     DATA: l_path  TYPE string,         l_sel   TYPE string,         lit_dyn TYPE TABLE OF dynpread,         lwa_dyn TYPE dynpread.   IF p_folder IS INITIAL.     lwa_dyn-fieldname = 'P_FOLDER'.     APPEND lwa_dyn TO lit_dyn.     CALL FUNCTION 'DYNP_VALUES_READ'       EXPORTING         dyname               = sy-cprog         dynumb               = sy-dynnr       TABLES         dynpfields           = lit_dyn       EXCEPTIONS         invalid_abapworkarea = 1         invalid_dynprofield  = 2         invalid_dynproname   = 3         invalid_dynpronummer = 4         invalid_request      = 5         no_fielddescription  = 6         invalid_parameter    = 7         undefind_error       = 8         double_conversion    = 9         stepl_not_found      = 10         OTHERS               = 11.       READ TABLE lit_dyn INTO lwa_dyn WITH KEY fieldname = 'P_FOLDER'.     l_path = lwa_dyn-fieldvalue.   ELSE.     l_path = p_folder.   ENDIF.   CALL METHOD cl_gui_frontend_services=>directory_browse     EXPORTING       initial_folder       = l_path     CHANGING       selected_folder      = l_sel     EXCEPTIONS       cntl_error           = 1       error_no_gui         = 2       not_supported_by_gui = 3       OTHERS               = 4.   IF sy-subrc EQ 0.     p_folder = l_sel.   ENDIF.   ENDFORM.

debug截图：

发现，虽然P_folder有初始默认值z:/zpkf，但是在VALUE-REQUEST事件中，P_folder为空,

随后通过DYNP_VALUES_READ读出，如下：

以上。