选择屏幕程序语法
1. PARAMETERS（见1.6）
SSCRFIELDS选择屏幕上的字段
USER-COMMAND fcode：在使按钮能正常工作之前，必须使用TABLES sscrfields.语句来为ABAP数据词典中的SSCRFIELDS结构来定义接口工作区。当用户点击按钮后会触发AT SELECTION-SCREEN事件，并且function code fcode会存储到sscrfields-ucomm字段中。
PARAMETERS: A1(10) TYPE C,
A2 TYPE I.
WRITE: / A1,/ A2.
2.SELECT-OPTIONS
SELECT-OPTIONS selcrit FOR {dobj|(name)}
[screen_options]
[value_options]
[ldb_options].
l screen_options
... [OBLIGATORY|NO-DISPLAY]
[VISIBLE LENGTH vlen]
[NO-EXTENSION] “限制选择表为单行，元素输入后面不会出现按钮。
[NO INTERVALS] ” 只会出现LOW字段，
[MODIF ID modid] ... . 选择屏幕中的参数选项 MEMORY ID的作用就等同于对话屏幕中的SET/GET Parameter，它们是作用是相同的（都是针对SAP Memory），只不过一个用于选择屏幕中，一个用于对话屏幕。
l value_options
... [DEFAULT val1 [TO val2] [OPTION opt] [SIGN sgn]]
[LOWER CASE]
[MATCHCODE OBJECT search_help]
[MEMORY ID pid] ... .
SELECT-OPTIONS selcrit FOR {dobj|(name)}
该语句会生成一个名为selcrit选择条件内表，行结构类型如下的全局内表：
DATA:BEGIN OF selcrit OCCURS 0,
sign(1), “sign字段是长度为1的C类型数据。它是标志位，允许值为I和E
option(2),” OPTION字段的数据类型是C，长度为2，OPTION包含选择运算符”
low LIKE mara-matnr, low字段的数据类型与f类型相同，该值为范围选择指定了下界
high LIKE mara-matnr, “HIGH字段的数据类型与f类型相同，该值为范围选择指定了上界
END OF selcrit.
语法示例：
s_werks FOR marc-werks OBLIGATORY DEFAULT 1001 to 1007 SIGN I OPTION BT
3.SELECT-SCREEN.
SELECTION-SCREEN - BEGIN OF SCREEN.
- 1. SELECTION-SCREEN BEGIN OF SCREEN dynnr [TITLE title]
[AS WINDOW].
SELECTION-SCREEN END OF SCREEN dynnr - SELECTION-SCREEN BEGIN OF SCREEN dynnr AS SUBSCREEN
[NO INTERVALS] 创建的框架中限制SELECT只有一个输入项
[NESTING LEVEL n]. adjust the width of the subscreen if it is to be included in a tabstrip control in one or more frames. You must specify n directly as a number between 0 and 4.
SELECTION-SCREEN END OF SCREEN dynnr.
SELECTION-SCREEN - screen_elements
1. SELECTION-SCREEN SKIP [n] [ldb_additions]. 空格n行
2. SELECTION-SCREEN ULINE [[/][pos](len)] [MODIF ID modid]
[ldb_additions]. 位置与长度，划出横线，必须用在BLOCK中才能生效
3. SELECTION-SCREEN COMMENT [/][pos](len)
{text|{[text] FOR FIELD sel}}
[VISIBLE LENGTH vlen]
[MODIF ID modid]
[ldb_additions].
4. SELECTION-SCREEN PUSHBUTTON [/][pos](len) button_text 位置与长度,名字
USER-COMMAND ucom 指定的字符代码，当用户在选择屏幕上触发按钮时
[VISIBLE LENGTH vlen]
[MODIF ID modid]
[ldb_additions].
5. SELECTION-SCREEN BEGIN OF LINE. 将所生成的屏幕元素控制在一行。
[SELECTION-SCREEN POSITION pos [ldb_additions]]. 在BLOCK中产生空格。
SELECTION-SCREEN END OF LINE.
6. SELECTION-SCREEN BEGIN OF BLOCK block
[WITH FRAME [TITLE title]]带标题框架
[NO INTERVALS].
SELECTION-SCREEN END OF BLOCK block.
7. SELECTION-SCREEN BEGIN OF TABBED BLOCK tblock FOR n LINES.
...
SELECTION-SCREEN TAB (len) tab USER-COMMAND ucom
[DEFAULT [PROGRAM prog] SCREEN dynnr].
...
SELECTION-SCREEN END OF BLOCK tblock.
8. SELECTION-SCREEN FUNCTION KEY n [ldb_additions]. the application toolbar contains five inactive pushbuttons, to which the function codes FC01 to FC05 are assigned. This statement activates the pushbutton of the function code FC0n, whereby a value between 1 and 5 must be entered for n.
语法示例：
示例一：
SELECTION-SCREEN BEGIN OF SCREEN 100 AS SUBSCREEN.
PARAMETERS: p1 TYPE c LENGTH 10,
p2 TYPE c LENGTH 10,
p3 TYPE c LENGTH 10.
SELECTION-SCREEN END OF SCREEN 100.
SELECTION-SCREEN BEGIN OF SCREEN 200 AS SUBSCREEN.
PARAMETERS: q1 TYPE c LENGTH 10,
q2 TYPE c LENGTH 10,
q3 TYPE c LENGTH 10.
SELECTION-SCREEN END OF SCREEN 200.
SELECTION-SCREEN: BEGIN OF TABBED BLOCK mytab FOR 10 LINES,
TAB (20) button1 USER-COMMAND push1,
TAB (20) button2 USER-COMMAND push2,
END OF BLOCK mytab.
INITIALIZATION.
button1 = 'Selection Screen 1'.
button2 = 'Selection Screen 2'.
mytab-prog = sy-repid.
mytab-dynnr = 100.
mytab-activetab = 'PUSH1'.
AT SELECTION-SCREEN.
CASE sy-dynnr. “当前屏幕号
WHEN 1000.
CASE sy-ucomm.
WHEN 'PUSH1'.
mytab-dynnr = 100.
WHEN 'PUSH2'.
mytab-dynnr = 200.
WHEN OTHERS.
ENDCASE.
ENDCASE.
示例二：
TYPE-POOLS icon.
TABLES sscrfields. “选择屏幕上的字段
DATA functxt TYPE smp_dyntxt. “动态文本的程序接口
PARAMETERS: p_carrid TYPE s_carr_id,
p_cityfr TYPE s_from_cit.
SELECTION-SCREEN: FUNCTION KEY 1, “FC01
FUNCTION KEY 2. “FC02
INITIALIZATION.
functxt-icon_id = icon_ws_plane.
functxt-quickinfo = 'Preselected Carrier'.
functxt-icon_text = 'LH'.
sscrfields-functxt_01 = functxt.
functxt-icon_text = 'UA'.
sscrfields-functxt_02 = functxt.
AT SELECTION-SCREEN.
CASE sscrfields-ucomm.
WHEN 'FC01'.
p_carrid = 'LH'.
p_cityfr = 'Frankfurt'.
WHEN 'FC02'.
p_carrid = 'UA'.
p_cityfr = 'Chicago'.
WHEN OTHERS.
ENDCASE.
SELECTION-SCREEN INCLUDE
(调用已经存在的屏幕元素)
PARAMETERSpara
[OBLIGATORY [OFF]]
[MODIF ID modid]
[ID id].
SELECT-OPTIONS selcrit
[OBLIGATORY [OFF]]
[NO INTERVALS [OFF]]
[NO-EXTENSIONS
[OFF]]
[MODIF ID modid]
[ID id].
COMMENT [/][pos](len) text
[FOR FIELD sel]
[MODIF ID modid]
[ID id].
PUSHBUTTON [/][pos](len) button_text
[USER-COMMAND ucom]
[MODIF ID modid]
[ID id].
BLOCKS block [ID id].
语法示例：
SELECTION-SCREEN: BEGIN OF BLOCK block,
COMMENT /1(40) text,
ULINE.
PARAMETERS: p1(10) TYPE c,
p2(10) TYPE c,
p3(10) TYPE c.
SELECTION-SCREEN END OF BLOCK block.
SELECTION-SCREEN: BEGIN OF SCREEN 500 AS WINDOW,
INCLUDE BLOCKS block,
END OF SCREEN 500.
INITIALIZATION.
text = 'Standard Selection'.
START-OF-SELECTION.
CALL SELECTION-SCREEN '0500' STARTING AT 10 10. “调用屏幕
CALL SELECTION-SCREEN
CALL SELECTION-SCREEN dynnr
[STARTING AT col1 lin1
[ENDING AT col2 lin2]]
[USING SELECTION-SET variant].
CALL SELECTION-SCREEN '0500' STARTING AT 10 10. “调用屏幕
AT SELECTION-SCREEN
是PAI处理，选择屏幕显示之后，用来响应回车，F8，F1，F4等事件。
（1）选择屏幕事件，此处声明的变量是局部变量。
（2）check sy-ucomm 判断用户命令。
（3）在这个事件响应中，可以对屏幕字段进行有效性检验等，但无法修改选择屏幕。
{ OUTPUT } 屏幕输出时的各屏幕元素值的管控（PBO处理，在选择屏幕显示之前就被调用；响应屏幕上的事件，用户回车或F8后也被调用；通过modify screen可以修改选择屏幕字段）
| { ON {para|selcrit} } 检查具体输入字段是否完整或正确
| { ON END OF selcrit }
| { ON BLOCK block }框架的触发事件（控制框架中的屏幕元素值的输入）
| { ON RADIOBUTTON GROUP radi }单选按钮事件，必须进行整体输入检查
| { }
| { ON {HELP-REQUEST|VALUE-REQUEST} VALUE-<F4>键时触发HELP-<F1>键时键
| FOR {para|selcrit-low|selcrit-high} }检查具体输入字段是否完整或正确
| { ON EXIT-COMMAND }.响应"BACK","CANCEL","EXIT"等事件
语法示例：
PARAMETERS p_carrid TYPE spfli-carrid.
AT SELECTION-SCREEN ON p_carrid.
IF p_carrid IS INITIAL.