sap的选择屏幕的标准工具栏上系统预先定义了5个按钮，他们对应的功能码是FC01-FC05，默认是不激活的。用户可以使用SELECTION-SCREEN FUNCTION KEY i.来激活这5个按钮（这里的i必须是1-5）,这五个按钮的文本放在SSCRFields的对应的Functxt_0i中。当用户按下按钮时，系统将触发AT SELECTION-SCREEN 事件,并将功能码放到sscrfields的ucomm字段中。
REPORT z_zcd_014.
TABLES sscrfields. "定义工作区
PARAMETERS: p_carrid TYPE s_carr_id,
p_cityfr TYPE s_from_cit.
SELECTION-SCREEN: FUNCTION KEY 1, "激活按钮
FUNCTION KEY 2.
INITIALIZATION.
sscrfields-functxt_01 = '@49@ 哈哈'.
sscrfields-functxt_02 = '@54@ 呵呵'.
AT SELECTION-SCREEN.
CASE sscrfields-ucomm. "处理按钮命令
WHEN'FC01'.
p_carrid = 'LH'.
p_cityfr = 'Frankfurt'.
WHEN 'FC02'.
p_carrid = 'UA'.
p_cityfr = 'Chicago'.
ENDCASE.
START-OF-SELECTION.
WRITE / 'START-OF-SELECTION'.
