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Screen Flow Logic Locate the document in its SAP Library structure

Screen flow logic contains the procedural part of a screen. You create it in the Structure linkflow logic editor in the Screen Painter, which is very similar to the ABAP Editor. The language used to program screen flow logic has a similar syntax to ABAP, but is not part of ABAP itself. It is sometimes referred to as screen language.

Unlike ABAP programs, screen flow logic contains no explicit data declarations. You define screen fields by placing elements on the screen mask.

The screen flow logic is like an ABAP program in that it serves as a container for processing blocks. There are four event blocks, each of which is introduced with the screen keyword PROCESS:

PROCESS BEFORE OUTPUT.
 ...

PROCESS AFTER INPUT.
 ...

PROCESS ON HELP-REQUEST.
 ...

PROCESS ON VALUE-REQUEST.
 ...

As in ABAP, the event block is introduced by the corresponding keyword statement, and it concludes either when the next block is introduced, or at the end of the program. The first two statements are created automatically by the Screen Painter when you create a new screen. The corresponding events are triggered by the runtime environment:

        PROCESS BEFORE OUTPUT (PBO) is automatically triggered after the PAI processing of the previous screen and before the current screen is displayed. You can program the PBO processing of the screen in this block. At the end of the PBO processing, the screen is displayed.

        PROCESS AFTER INPUT (PAI) is triggered when the user chooses a function on the screen. You can program the PAI processing of the screen in this block. At the end of the PAI processing, the system either calls the next screen or carries on processing at the point from which the screen was called.

        PROCESS ON HELP-REQUEST (POH) and PROCESS ON VALUE-REQUEST (POV) are triggered when the user requests field help (F1) or possible values help (F4) respectively. You can program the appropriate coding in the corresponding event blocks. At the end of processing, the system carries on processing the current screen.

As is normal with events, you must only program event blocks for the events to which you want the flow logic to react. However, the screen flow logic must contain at least the two statements PROCESS BEFORE OUTPUT and PROCESS AFTER INPUT in the correct order.

Within the event blocks, you can use the following screen-keywords:

Keyword

Description

MODULE

Calls a dialog module in an ABAP program

FIELD

Specifies the point at which the contents of a screen field should be transported

 

ON

Used in conjunction with FIELD

VALUES

Used in conjunction with FIELD

CHAIN

Starts a processing chain.

ENDCHAIN

Ends a processing chain.

CALL

Calls a subscreen.

LOOP

Starts processing a screen table

ENDLOOP

Ends processing a screen table

The functions of the individual statements are described in the following sections.

 

 

 

 

 

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