1 在GUI状态里添加自定义的按钮，保存、激活；

2 修改代码：

（1）自定义的按钮的触发在 FRM_USER_COMMAND 这个模块里面。

（2）这里注意 FRM_USER_COMMAND 的参数是两个，把自定义的按钮和触发后的操作写在CASE里面。

 3 效果展示如下:

贴一下完整代码：

FORM display_data .
* alv 显示定义
  DATA: i_grid_settings TYPE lvc_s_glay,
        lt_fieldcat     TYPE slis_t_fieldcat_alv,
        lr_aggregations TYPE REF TO cl_salv_aggregations.
  DATA:gt_fieldcat TYPE slis_t_fieldcat_alv WITH HEADER LINE,
       gs_layout   TYPE slis_layout_alv.

* 自定义ALV 显示方式
  DEFINE fill_alv.
    clear gt_fieldcat.
    gt_fieldcat-fieldname = &1.  "变量1 字段名
    gt_fieldcat-seltext_m = &2 .  "变量2 字段描述
    gt_fieldcat-outputlen = &3 .  "变量2 字段描述
    gt_fieldcat-NO_ZERO = &4.
    append gt_fieldcat.
  END-OF-DEFINITION.
  fill_alv 'CARRID' '航线代码' '3' 'X'.
  fill_alv 'AIRPFROM' '起飞机场' '3' 'X'.
  fill_alv 'CONNID' '航线连接' '4' 'X'.
  fill_alv 'FLTIME' '航班时间' '10' 'X'.
  fill_alv 'CITYFROM' '起飞城市' '20' 'X'.
  fill_alv 'CITYTO' '目标城市' '20' 'X'.

  LOOP AT gt_fieldcat.
    MODIFY gt_fieldcat.
    IF gt_fieldcat-fieldname = ' FLTIME'.
      gt_fieldcat-edit = 'X'.
      gt_fieldcat-outputlen = '50'.
    ENDIF.
    MODIFY gt_fieldcat.
  ENDLOOP.

  i_grid_settings-edt_cll_cb = 'X'. "退出可编辑单元格时回调

  gs_layout-zebra        = 'X'.
  gs_layout-colwidth_optimize = 'X'.
  gs_layout-box_fieldname = 'ZSEL'. "定义边框选中栏
  gs_layout-window_titlebar = '查询表'.

  CALL FUNCTION 'REUSE_ALV_GRID_DISPLAY'
    EXPORTING
      i_callback_program       = sy-repid
      i_callback_pf_status_set = 'SET_PF_STATUS'
      i_callback_user_command  = 'FRM_USER_COMMAND'
      i_grid_settings          = i_grid_settings
      is_layout                = gs_layout
      it_fieldcat              = gt_fieldcat[]
      it_sort                  = lt_sort
*     it_events                = i_events
      i_save                   = 'A'
    TABLES
      t_outtab                 = gt_tab
    EXCEPTIONS
      program_error            = 1
      OTHERS                   = 2.

ENDFORM.                    " DISPLAY_DATA


FORM frm_user_command USING ucomm TYPE sy-ucomm
                            p_selfld TYPE slis_selfield.
  CASE ucomm.
    WHEN '&BACK'.
      leave to screen 0.
  ENDCASE.

ENDFORM.

总结：自定义按钮体现在i_callback_user_command  = 'FRM_USER_COMMAND' 中，其中FRM_USER_COMMAND是自定义的过程。