让文件选择窗口支持多个文件类型

一晃都九月了, 有日子没发东西了, 随便发点东西

本例同时支持XLS和XLSX文件,

  CALL METHOD cl_gui_frontend_services=>file_open_dialog
    EXPORTING
      window_title     = 'Please Select an Excel File'
      file_filter      = '(*.xls)|*.xls|(*.xlsx)|*.xlsx'
      multiselection   = ''
    CHANGING
      file_table       = gt_tab
      rc               = gv_subrc.