ABAP/4 How to trigger start of selection after pressing pushbutton from report

在 Report 使用 PUSHBUTTON，有時會希望透過 AT SELECTION-SCREEN. 處理一些前置功能後再進入 START-OF-SELECTION。

但實際使用 PUSHBUTTON 後，會發現按下按鈕後，只會執行 AT SELECTION-SCREEN. 無法再進入 START-OF-SELECTION，如下圖，按執行的 ICON 才會進入 START-OF-SELECTION，但只按 PUSHBUTTON 並不會進入 START-OF-SELECTION。

REPORT Z_ABAP_22_PBTN_TRIGGER_START.

SELECTION-SCREEN BEGIN OF LINE.
SELECTION-SCREEN PUSHBUTTON (40) W_BUT1 USER-COMMAND BUT1.
SELECTION-SCREEN END OF LINE.

INITIALIZATION.
  W_BUT1 = 'PUSHBUTTON'.

AT SELECTION-SCREEN.
  CASE sy-ucomm.
    WHEN 'BUT1'.
      MESSAGE 'AT SELECTION SCREEN' TYPE 'I'.
  ENDCASE.

START-OF-SELECTION.
  MESSAGE 'START-OF-SELECTION' TYPE 'I'.
END-OF-SELECTION.

而執行進入 START-OF-SELECTION 的 command 是 'ONLI'，所以可以再執行時把 sy-ucomm 與 sscrfields-ucomm 強制改成 'ONLI'，即可由 AT SELECTION-SCREEN 執行後，再觸發 START-OF-SELECTION

REPORT Z_ABAP_22_PBTN_TRIGGER_START.

TABLES sscrfields.

SELECTION-SCREEN BEGIN OF LINE.
SELECTION-SCREEN PUSHBUTTON (40) W_BUT1 USER-COMMAND BUT1.
SELECTION-SCREEN END OF LINE.

INITIALIZATION.
  W_BUT1 = 'PUSHBUTTON'.

AT SELECTION-SCREEN.
  CASE sy-ucomm.
    WHEN 'BUT1'.
      sy-ucomm = 'ONLI'.
      sscrfields-ucomm = 'ONLI'.
      MESSAGE 'AT SELECTION SCREEN' TYPE 'I'.
  ENDCASE.

START-OF-SELECTION.
  MESSAGE 'START-OF-SELECTION' TYPE 'I'.
END-OF-SELECTION.

加入上面紅字後，即可先觸發 AT SELECTION SCREEN 後，再觸發 START-OF-SELECTION