abap user_command 报错A new value is to be assigned to the field "", although this field is entirely or partly protected against changes. The following are protected from change: - Character literals or numerical literals. - CONSTANTS. - Parameters

abap user_command 报错A new value is to be assigned to the field "", although this field is entirely or partly protected against changes. The following are protected from change: - Character literals or numerical literals. - CONSTANTS. - Parameters
abap user_command 报错
A new value is to be assigned to the field "", although this field is
entirely or partly protected against changes.
The following are protected from change:
- Character literals or numerical literals.
- CONSTANTS.
- Parameters of the category IMPORTING REFERENCE in functions and
methods.
- untyped field symbols, that have not been assigned a field using
ASSIGN.
- TABLES parameters, if the actual parameter is protected against
changes.
- USING reference parameters and CHANGING parameters in FORMs,
if the actual parameter is protected against changes.
- Access using field symbols if the field assigned using ASSIGN is
partly or completely protected (for example key components of internal
table of the type SORTED or HASHED TABLE).
- Access using field symbols if the field assigned using ASSIGN contains

components of a secondary key that is currently in use in a
higher-level LOOP statement.
Access using references if the field bound to the reference is
(partly) protected against changes.
Write access from outside to READ-ONLY attributes.
Content of a shared objects area instance accessed using a shared lock
(ATTACH_FOR_READ.
Rows or fields of a table that are currently being serialized by a
Simple Transformation.
部分代码如下
FORM USER_COMMAND USING R_UCOMM LIKE SY-UCOMM
RS_SELFIELD TYPE SLIS_SELFIELD.
错误老是指向后台这里 一下为部分后台代码
* set/unset of all items
if l_ucomm eq '&SAL' or l_ucomm eq '&ALL'.
if l_ucomm eq '&SAL'.
loop at t_outtab.
l_tabix = l_tabix + 1.
= ' '.
modify t_outtab index l_tabix.
endloop.
endif.
调试 程序走到 = ' '. 这里就报错了

abap user_command 报错A new value is to be assigned to the field "", although this field is entirely or partly protected against changes. The following are protected from change: - Character literals or numerical literals. - CONSTANTS. - Parameters
仅通过你提供的信息是没办法找到问题原因的,你可以把ST22的截图给附加上来,这个问题应该是SAP标准程序报出的错误,需要根据ST22里面的提示,如果有需要可能要上Service网上查Notes