SAP选择屏幕中实现三级联动下拉框效果

主程序代码：

1. TYPE-POOLS:VRM.
   
2. DATA: NAME TYPE VRM_ID.
   
3. DATA:NUM TYPE I. "根据PRODH字段长度判断 某行属于哪一级
   
4. DATA:LOADED TYPE C LENGTH 1."控制不重复查询数据库和不反复append数据 to WA1[]
   
5. 
   
6. TYPES: BEGIN OF WA,
   
7.    KEY(40),
   
8.    TEXT(80) TYPE C,
   
9. END OF WA.
   
10. DATA:GT LIKE T179T OCCURS 0 WITH HEADER LINE.
    
11. DATA:WA1 TYPE TABLE OF WA WITH HEADER LINE."111
    
12. DATA:WA2 TYPE TABLE OF WA WITH HEADER LINE.                 "111222
    
13. DATA:WA3 TYPE TABLE OF WA WITH HEADER LINE.                 "111222333
    
14. 
    
15. DATA:ITAB LIKE T179T OCCURS 0 WITH HEADER LINE.
    
16. DATA: PS_T(15) TYPE C.
    
17. SELECTION-SCREEN BEGIN OF BLOCK T1 WITH FRAME TITLE TEXT-001.
    
18. 
    
19. SELECTION-SCREEN BEGIN OF LINE.
    
20. SELECTION-SCREEN COMMENT 1(31) TEXT-003.
    
21. PARAMETERS: PL1 LIKE PS_T AS LISTBOX VISIBLE LENGTH 15 USER-COMMAND P1.
    
22. "一级类
    
23. SELECTION-SCREEN END OF LINE.
    
24. SELECTION-SCREEN SKIP 1.
    
25. 
    
26. SELECTION-SCREEN BEGIN OF LINE.
    
27. SELECTION-SCREEN COMMENT 1(31) TEXT-004.
    
28. PARAMETERS: PL2 LIKE PS_T AS LISTBOX VISIBLE LENGTH 15 USER-COMMAND P2.
    
29. "二级类
    
30. SELECTION-SCREEN END OF LINE.
    
31. SELECTION-SCREEN SKIP 1.
    
32. 
    
33. SELECTION-SCREEN BEGIN OF LINE.
    
34. SELECTION-SCREEN COMMENT 1(31) TEXT-005.
    
35. PARAMETERS: PL3 LIKE PS_T AS LISTBOX VISIBLE LENGTH 15.
    
36. "三级类
    
37. SELECTION-SCREEN END OF LINE.
    
38. 
    
39. SELECTION-SCREEN END OF BLOCK T1.
    
40. 
    
41. INITIALIZATION.
    
42. 
    
43. 
    
44. AT SELECTION-SCREEN OUTPUT.
    
45.   NAME = 'PL1'.
    
46.   IF LOADED  IS INITIAL.
    
47.   SELECT *  FROM T179T INTO TABLE GT  WHERE SPRAS = 1.
    
48.   LOADED = 'X'.
    
49.   LOOP AT GT.
    
50.     NUM = STRLEN( GT-PRODH ).
    
51.     IF NUM = 5.
    
52.       WA1-TEXT  = GT-VTEXT."Description
    
53.       WA1-KEY   = GT-PRODH."Product hierarchy   key field
    
54.       APPEND: WA1.
    
55.     ENDIF.
    
56.     CLEAR: GT,NUM,WA1."CLEAR 清空WA1工作区，不清空WA1[]内表
    
57.   ENDLOOP.
    
58.   ENDIF.
    
59. 
    
60. 
    
61. 
    
62.   CALL FUNCTION 'VRM_SET_VALUES'
    
63.     EXPORTING
    
64.       ID     = NAME
    
65.       VALUES = WA1[].
    
66. 
    
67. 
    
68. AT SELECTION-SCREEN.
    
69. 
    
70.   CASE SY-UCOMM.
    
71.     WHEN 'P1'.
    
72.       CLEAR: PL2,PL3.
    
73.       "清空2、3级下拉空默认值，当用户在选择屏幕上重新选择时需要清除
    
74.       CLEAR:WA2,WA2[].
    
75.       "清空2级下拉内表对应的值，当用户在选择屏幕上重新选择时需要清除
    
76.       CLEAR NUM.
    
77.       LOOP AT GT .
    
78.         NUM = STRLEN( GT-PRODH ).
    
79.         IF NUM = 10 AND GT-PRODH+0(5) = PL1.
    
80. 
    
81.           WA2-TEXT  = GT-VTEXT.
    
82.           WA2-KEY   = GT-PRODH.
    
83.           APPEND: WA2.
    
84. 
    
85.         ENDIF.
    
86.         CLEAR:GT,NUM,WA2.
    
87.       ENDLOOP.
    
88. 
    
89.       CALL FUNCTION 'VRM_SET_VALUES'
    
90.         EXPORTING
    
91.           ID     = 'PL2'
    
92.           VALUES = WA2[].
    
93.       CLEAR PL2.
    
94.     WHEN 'P2'.
    
95.       CLEAR PL3.
    
96.       "清空3级下拉空默认值，当用户在选择屏幕上重新选择时需要清除
    
97.       CLEAR:WA3,WA3[].
    
98.       "清空3级下拉内表对应的值，当用户在选择屏幕上重新选择时需要清除
    
99.       CLEAR NUM.
    
100.       LOOP AT GT .
     
101.         NUM = STRLEN( GT-PRODH ).
     
102.         IF NUM = 18 AND GT-PRODH+0(10) = PL2.
     
103. 
     
104.           WA3-TEXT  = GT-VTEXT.
     
105.           WA3-KEY   = GT-PRODH.
     
106.           APPEND: WA3.
     
107. 
     
108.         ENDIF.
     
109.         CLEAR:GT,NUM,WA3.
     
110.       ENDLOOP.
     
111. 
     
112.       CALL FUNCTION 'VRM_SET_VALUES'
     
113.         EXPORTING
     
114.           ID     = 'PL3'
     
115.           VALUES = WA3[].
     
116.       CLEAR PL3.
     
117.   ENDCASE.

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执行效果：
选择父

选择子

选择孙

学习了。