ABAP CHECKBOX 和LISTBOX使用指南

   1.什么是checkbox：
    就是一个复选框，可以用like或者type来定义，为1个字符型变量。它是parameter的一个选项，parameter xxx as checkbox就可以在选择屏幕上显示一个复选框。
    2.什么是listbox：
    就是一个下拉列表，你可以在这个列表中选择一条记录进行某种操作。也是parameter的一个选项，parameter xxx as listbox就可以在选择屏幕上显示一个下拉列表。
    3.如何使用：
    下面我们用一个程序来说明这两者的使用方法。    REPORT Z_TEXT
    TYPE-POOLS: VRM .  “存放combobox内容的type pool
    DATA: NAME TYPE VRM_ID ,        “ list box的名称
          LIST TYPE VRM_VALUES ,    “ list box的值
          VALUE LIKE LINE OF LIST . “ list box的结构
    *定义checkbox，指定command，为了能够响应选择屏幕中值的改变
    PARAMETERS: P_CB1 TYPE C AS CHECKBOX DEFAULT 'X' USER-COMMAND CHECK,
                P_CB2 TYPE C AS CHECKBOX DEFAULT 'X' USER-COMMAND CHECK.
    *定义listbox，必须指定visible length
    PARAMETERS: P_LIST1(10) TYPE C AS LISTBOX
                                      VISIBLE LENGTH 15 ,
                P_LIST2(20) TYPE C    AS LISTBOX
                                      VISIBLE LENGTH 25 .
    *开始执行
    AT SELECTION-SCREEN OUTPUT .
    *--〉选择1而没有选择2
      IF P_CB1 = 'X' AND P_CB2 = ''.
    *---〉向listbox里面添加值
        REFRESH LIST .
        VALUE-KEY = '1111' .     “这个就是变量P_LIST的值
        VALUE-TEXT = '1111' .    “这个是text
        APPEND VALUE TO LIST .
        VALUE-KEY = '2222222222' .
        VALUE-TEXT = '2222222222' .
        APPEND VALUE TO LIST .
        VALUE-KEY = '3333333333' .
        VALUE-TEXT = '3333333333' .
        APPEND VALUE TO LIST .
    *---〉调用函数显示listbox里面的值
        CALL FUNCTION 'VRM_SET_VALUES'
          EXPORTING
            ID     = 'P_LIST1'
            VALUES = LIST.
    *---〉把第二个listbox的值清空，并且不能输入
        CLEAR P_LIST2 .
        LOOP AT SCREEN .
          IF SCREEN-NAME = 'P_LIST2' .
            SCREEN-INPUT = 0 .
            MODIFY SCREEN .
          ENDIF .
        ENDLOOP .
    *--〉选择2，没有选择1，同上
      ELSEIF P_CB2 = 'X' AND P_CB1 = ''.
        REFRESH LIST .
        VALUE-KEY = 'AAAAAAAAAAAAAAAAAAAA' .
        VALUE-TEXT = 'AAAAAAAAAAAAAAAAAAAA' .
        APPEND VALUE TO LIST .
        VALUE-KEY = 'BBBBBBBBBBBBBBBBBBBB' .
        VALUE-TEXT = 'BBBBBBBBBBBBBBBBBBBB' .
        APPEND VALUE TO LIST .
        VALUE-KEY = 'CCCCCCCCCCCCCCCCCCCC' .
        VALUE-TEXT = 'CCCCCCCCCCCCCCCCCCCC' .
        APPEND VALUE TO LIST .
        APPEND VALUE TO LIST .
        CALL FUNCTION 'VRM_SET_VALUES'
          EXPORTING
            ID     = 'P_LIST2'
            VALUES = LIST.
    *---〉清空listbox 1的值
        CLEAR P_LIST1 .
        LOOP AT SCREEN .
          IF SCREEN-NAME = 'P_LIST1' .
            SCREEN-INPUT = 0 .
            MODIFY SCREEN .
          ENDIF .
        ENDLOOP .
    *--〉都没有选择，都清空且不能输入
      ELSEIF P_CB1 = '' AND P_CB2 = '' .
        CLEAR: P_LIST1,P_LIST2 .
        LOOP AT SCREEN .
          IF SCREEN-NAME = 'P_LIST1' .
            SCREEN-INPUT = 0 .
            MODIFY SCREEN .
          ENDIF .
        ENDLOOP .
        LOOP AT SCREEN .
          IF SCREEN-NAME = 'P_LIST2' .
            SCREEN-INPUT = 0 .
            MODIFY SCREEN .
          ENDIF .
        ENDLOOP .
    *--〉都选，执行
      ELSEIF P_CB1 = 'X' AND P_CB2 = 'X' .
        REFRESH LIST .
        VALUE-KEY = '1111' .
        VALUE-TEXT = '1111' .
        APPEND VALUE TO LIST .
        VALUE-KEY = '2222222222' .
        VALUE-TEXT = '2222222222' .
        APPEND VALUE TO LIST .
        VALUE-KEY = '3333333333' .
        VALUE-TEXT = '3333333333' .
        APPEND VALUE TO LIST .
        CALL FUNCTION 'VRM_SET_VALUES'
          EXPORTING
            ID     = 'P_LIST1'
            VALUES = LIST.
        REFRESH LIST .
        VALUE-KEY = 'AAAAAAAAAAAAAAAAAAAA' .
        VALUE-TEXT = 'AAAAAAAAAAAAAAAAAAAA' .
        APPEND VALUE TO LIST .
        VALUE-KEY = 'BBBBBBBBBBBBBBBBBBBB' .
        VALUE-TEXT = 'BBBBBBBBBBBBBBBBBBBB' .
        APPEND VALUE TO LIST .
        VALUE-KEY = 'CCCCCCCCCCCCCCCCCCCC' .
        VALUE-TEXT = 'CCCCCCCCCCCCCCCCCCCC' .
        APPEND VALUE TO LIST .
        CALL FUNCTION 'VRM_SET_VALUES'
          EXPORTING
            ID     = 'P_LIST2'
            VALUES = LIST.
      ENDIF .
    START-OF-SELECTION .
    *--〉输出到第二屏幕看看
      WRITE:  P_LIST1 ,/ P_LIST2 .