http://abaper.cn/admin/admin_default.asp
http://www.sapdev.co.uk/reporting/alv/alv_variousfcat.htm
1. OO ALV 不能直接通过函数获得alv的field catalog，只有用FM的方式获得itab的fieldcatalog然后转换成OO的 TABLES: LVC_S_FCAT.
TYPE-POOLS: SLIS.
DATA: GT_FIELDCATALOG TYPE SLIS_T_FIELDCAT_ALV WITH HEADER LINE.
DATA: GT_REPID TYPE SY-REPID.
GT_REPID = SY-REPID.
CALL FUNCTION 'REUSE_ALV_FIELDCATALOG_MERGE'
EXPORTING
I_PROGRAM_NAME = GT_REPID
I_INTERNAL_TABNAME = 'ITAB'
I_INCLNAME = GT_REPID
CHANGING
CT_FIELDCAT = GT_FIELDCATALOG[].
DATA: GT_LVC_FIELDCATALOG TYPE LVC_T_FCAT.
LOOP AT GT_FIELDCATALOG.
MOVE-CORRESPONDING GT_FIELDCATALOG TO LVC_S_FCAT.
APPEND LVC_S_FCAT TO GT_LVC_FIELDCATALOG.
ENDLOOP.
http://help.sap.com/saphelp_bw/helpdata/en/52/5f060de02d11d2b47d006094192fe3/content.htm
| Output table fields with DDIC reference | Output table fields without DDIC reference | Explanation |
| FIELDNAME | FIELDNAME | Name of the field of the internal output table |
| REF_TABNAME | Name of the DDIC reference structure | |
| REF_FIELDNAME | Name of the DDIC reference field (only needed if other than FIELDNAME ) | |
| INTTYPE | ABAP data type of the field of the internal output table | |
| OUTPUTLEN | Column width | |
| COLTEXT | Column header | |
| SELTEXT | Column description in column selection for layout |
