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Step-loops in Module Pool Programming
Step-loops in Module Pool Programming
Step-loops are actually the predecessors to Table Control
concepts and from programming point of
view they are quite similar. Step loops are objects for screen
table display that are added to a screenin the Screen Painter. They
are preferred in cases of Radio-frequency applications where
ALVdisplays or table controls pose a hindrance with respect to
small displays and navigational issues.
1. Introduction to Step Loops
This article throws light on the concept of Step-loops in Module
screen programming. Step-loops are avery old concept and their use
has been drastically reduced after the onset of Table control. But
incertain applications such as Radio Frequency there is no other
alternative than using step-loops.
The pre-requisite to understanding and design of step-loops is
to have a fair idea over module poolprogramming.
Step-loops are of 2 types:
Fixed Step-loopsIncase of Fixed step-loops, the number of lines
of records would be fixed as when designed. You canincrease the
number of records at runtime. Although the number of records can be
decreased as perprogramming logic if number of records in table to
be displayed are less than fixed number.
Variable Step-loopsIn case of variable step-loops, at runtime we
can increase the number of repetitive blocks dependingon the size
of the screen.
2. Requirement to be designed
We will look into a requirement where we have display records in
a step-loop on screen in such amanner that we will keep the
step-loop fixed to 5 rows for simplicity and based on the number
ofrecords; the records will flow onto the next screens.
Also if there are only 2 records to be displayed then only 2
rows will appear on the screen with nobuttons for navigation. So
the navigation buttons Page Up and Page Down would be
handlingdynamically based on the records to be displayed.
3. How to design Step-loops?
A step loop is defined in the screen painter transaction SE51;
these are unlike the table controlelements which can be spread over
multiple lines and can be combined into one group which wouldbe
repeated within the step loop. It is important to note that
whichever attributes we assign to the firstgroup are replicated to
the entire step loop.
In thescreen painter, we can define whether the size of a step
loop is fixed or variable. The verticalsize of variable step loops
changes if the user changes the vertical size of the window. For
everyscreen, any number of fixed step loops can be defined but only
one variable step loop. Every verticalsize change triggers PAI if a
variable step loop is defined on the screen. For fixed step loops
thenumber of repetition groups has to be predefined.
To place step-loops in the module pool screen, we need to place
input/output fields for the number ofcolumns required and
text-fields for the number of column headers. As described, we
would first place
the input-output fields and text-fields as per the number of
columns to be displayed as shown below:
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Later in order to convert these into step-loops, select the
input/output fields together for all requiredcolumns and follow the
steps as shown below in the screenshot with the menu path as Edit
->Grouping -> Step Loop -> Define.
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In the below screenshot, Column1 and Column2 denote the column
headers, Page up and Down arethe buttons which would help us in
scrolling the records. In this case we have kept step-loop as
fixedup to 5 rows for simplicity. The column1 and column 2 are
simple text fields.
On double Clicking you will find the following step-loop
property where Height is restricted to 5 rows.See below
screenshot.
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The step-loop column field properties would be as below:
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The buttons Page up and Page down would be given function codes
as PGUP and PGDN and theirproperties would be as follows:
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4. Flow-logic for Step-loops
Once the processing for the records to be displayed is done,
then in the flow logic of the screen 0100which we have designed we
need to include the code shown below:
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Its important to note that the LOOP must exist for every step
loop, both in the PBO and the PAIprocessing block. During the
loops, the contents of the step loop are transported back and
forthbetween identically-named fields of the ABAP program and the
screen. Note that step loop fieldsdefined with Dictionary reference
must be defined in the ABAP program, as before, with TABLES
asinterface work areas. The order the step loops are processed in
the individual loops of the flow logicdepends on the step loop
order on the screen. The order on the screen depends primarily on
the linesand secondarily on the rows. The system fields SY-STPL and
SY-LOOPC are also filled within theloops.
In the PBO module we have looped the cursor C from N1 to N2
since we want to display on screenonly as many as rows as many
number of records are there to be present on the screen. Thus if
thereare only 2 records then N1 = 1 and N2 =2; so that 2 step loops
appear on the screen. This wouldensure dynamicity of the
step-loops.
The table structure for the records to be displayed in
step-loops would be as follows:
a. The module STATUS_0100 would contain the PF status and PF
Title to be maintained in thescreen.
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In the PF status needs to be activated for function keys BACK,
PGUP and PGDNso that these buttons on the keyboard can be used and
so also on the Radio-frequency (RF)application handset.
b. The module PGUP_DOWN contains the logic for navigation from
one page to anotherdepending on the number of records to be
displayed.
This would basically contain the logic to hide/show the buttons
for page up and downdepending on the records which overflow on the
page. For example, on first page the buttonfor page up would be
hidden and on last page the button for page down would be
hidden.
c. The module TRANSP_ITAB_OUT contains the logic to transfer the
contents of the internaltable into the step-loop screen elements
during PBO processing.
d. The module TRANSP_ITAB_IN contains the logic to transfer the
contents from internal tableinto the step-loop screen elements
during PAI processing.
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e. The module USER_COMMAND_0100 would help to handle the
navigation and processing atthe click on the buttons Page Up and
Page Down. Please see source code extract for furtherdetails for
handling the button clicks.
REPORT ystep_loop_test.
* Number of records to be displayedPARAMETERS : p_num TYPE
i.
* Types to declare the internal table for recordsTYPES: BEGIN OF
t_itab,
col1 TYPE i,col2 TYPE i,
END OF t_itab.* Internal table for the recordsDATA: itab TYPE
STANDARD TABLE OF t_itab,* Work area for the records
wa LIKE LINE OF itab.DATA:
* Index of the row of step-loopidx TYPE i,
* Current Line to be displayedline TYPE i,
* Total Rows of step-loop to be displayed on single pagelines
TYPE i,
* Final Limit of step loop rows that can be displayedlimit TYPE
i,
* Cursor positionc TYPE i,
* Lower limit of the record index to be displayed on a pagen1
TYPE i VALUE 1,
* Upper limit of the record index to be displayed on a page
n2 TYPE i,* Variable to handle next page navigationy_v_next TYPE
i,
* Variable to handle previous page navigationy_v_prev TYPE
i,y_v_limit TYPE i.
DATA: ok_code TYPE sy-ucomm,save_ok TYPE sy-ucomm.
START-OF-SELECTION.
* Building the records to be displayed as per the selection
screen entry
DO p_num TIMES.wa-col1 = sy-index.wa-col2 = sy-index ** 2.APPEND
wa TO itab.
ENDDO.
IF p_num < 0.n2 = p_num.
ELSE.n2 = 5.
ENDIF.
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CALL SCREEN
100.*----------------------------------------------------------------------**
MODULE status_0100
OUTPUT*----------------------------------------------------------------------***----------------------------------------------------------------------*
MODULE status_0100 OUTPUT.SET PF-STATUS 'STATUS_100'.ENDMODULE.
"status_0100
OUTPUT*----------------------------------------------------------------------**
MODULE transp_itab_out
OUTPUT*----------------------------------------------------------------------***----------------------------------------------------------------------*MODULE
transp_itab_out OUTPUT.idx = sy-stepl + line.READ TABLE itab INTO
wa INDEX idx.
ENDMODULE. "transp_itab_out
OUTPUT*----------------------------------------------------------------------*
* MODULE transp_itab_in
INPUT*----------------------------------------------------------------------***----------------------------------------------------------------------*MODULE
transp_itab_in INPUT.lines = sy-loopc.idx = sy-stepl + line.MODIFY
itab FROM wa INDEX idx.
ENDMODULE. "transp_itab_in
INPUT*----------------------------------------------------------------------**
MODULE user_command_0100
INPUT*----------------------------------------------------------------------***----------------------------------------------------------------------*MODULE
user_command_0100 INPUT.DATA : y_v_index TYPE sy-index.DATA :
y_lv_d TYPE f,
y_lv_div TYPE i,y_curr_p_num TYPE i.
save_ok = ok_code.CLEAR ok_code.CASE save_ok.WHEN 'BACK'.LEAVE
TO SCREEN 0.
* When Page Down is HitWHEN 'PGDN'.
* Number of screens required for output if 5 records per
screeny_lv_d = p_num / 5.y_lv_div = CEIL( y_lv_d ).y_curr_p_num =
y_lv_div * 5.y_v_index = y_v_next + 1.IF y_v_next <
y_lv_div.y_v_next = y_v_next + 1.
ELSE.y_v_next = y_lv_div.
ENDIF.y_v_prev = y_v_next.IF y_v_next y_lv_div.n2 = p_num - 5 *
y_v_next.IF n2 > 5.
n2 = 5 * y_v_next.ENDIF.n1 = 1.
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line = line + lines.limit = y_curr_p_num - lines.IF line >
limit.line = limit.
ENDIF.ELSE.
y_v_next = y_v_next - 1.ENDIF.* When Page Up is Hit
WHEN 'PGUP'.n2 = 5 * y_v_next.IF n1 < 0.n1 = 1.
ENDIF.IF y_v_next > 0.y_v_next = y_v_next - 1.
ELSE.y_v_next = 0.
ENDIF.
y_v_prev = y_v_next.IF line NE 0 AND y_curr_p_num GT 5.line =
y_v_next * 5.
ELSE.line = 0.y_v_index = y_v_next - 1.
ENDIF.IF line < 0.line = 0.
ENDIF.ENDCASE.
ENDMODULE. "user_command_0100
INPUT*----------------------------------------------------------------------**
MODULE cancel
INPUT*----------------------------------------------------------------------***----------------------------------------------------------------------*MODULE
cancel INPUT.LEAVE PROGRAM.
ENDMODULE. "cancel
INPUT*&---------------------------------------------------------------------**&
Module PGUP_DOWN
OUTPUT*&---------------------------------------------------------------------**
text*----------------------------------------------------------------------*MODULE
pgup_down OUTPUT.DATA : y_v_div TYPE i,
y_v_d TYPE f,y_v_temp TYPE i.
DESCRIBE TABLE itab[] LINES p_num.y_v_d = p_num / 5.y_v_limit =
CEIL( y_v_d ).y_v_temp = y_v_limit - 1.IF p_num LE 5.PERFORM
y_f_hide_field USING 'RLMOB-PPGDN'.PERFORM y_f_hide_field USING
'RLMOB-PPGUP'.
ELSEIF y_v_next = y_v_limit .PERFORM y_f_hide_field USING
'RLMOB-PPGDN'.PERFORM y_f_show_field USING 'RLMOB-PPGUP'.
ELSEIF y_v_prev IS INITIAL.
PERFORM y_f_hide_field USING 'RLMOB-PPGUP'.ELSEIF y_v_next GT
y_v_limit.PERFORM y_f_hide_field USING 'RLMOB-PPGDN'.
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ELSEIF y_v_temp = y_v_next.PERFORM y_f_hide_field USING
'RLMOB-PPGDN'.
ENDIF.ENDMODULE. " PGUP_DOWN
OUTPUT*&---------------------------------------------------------------------**&
Form Y_F_HIDE_FIELD
*&---------------------------------------------------------------------**
text*----------------------------------------------------------------------**
-->P_0372
text*----------------------------------------------------------------------*FORM
y_f_hide_field USING value(p_name).LOOP AT SCREEN.IF screen-name =
p_name.screen-active = '0'.screen-invisible = '1'.MODIFY
SCREEN.EXIT.
ENDIF.
ENDLOOP.ENDFORM. "
Y_F_HIDE_FIELD*&---------------------------------------------------------------------**&
Form
Y_F_SHOW_FIELD*&---------------------------------------------------------------------**
text*----------------------------------------------------------------------**
-->P_0388
text*----------------------------------------------------------------------*FORM
y_f_show_field USING value(p_name).LOOP AT SCREEN.IF screen-name =
p_name.screen-active = '1'.MODIFY SCREEN.EXIT.
ENDIF.ENDLOOP.
ENDFORM. " Y_F_SHOW_FIELD
