BUS-Screen Framework - A short introduction

[TudorRiscutia]

In a world of Web Dynpro and cool UI5 libraries, I still find myself working with ABAP Reports and classic Dynpros. Being a techie, it is easy to imagine why I don't see these kinds of tasks very intriguing. Yet I wish to make it interesting by exploring modern (and better) ways to improve development.

So... This is a short guide on how to implement an ABAP report using the BUS-Screen Framework. Although this was initially intended for internal SAP usage only, it is not publicly available.

Misconception

If you search online on how to use BUS-Screen Framework, besides not getting a lot of results, you will also get some wrongful information. BUS-Screen Framework cannot dynamically create Dynpros. It is merely a way to structure reports in an object-oriented way.

Still interested? ... Great!

First and foremost, I have to recommend the book Anwendungsentwicklung mit ABAP Objects by Thorsten Franz and Tobias Trapp, which contains a whole subchapter dedicated to the BUS-Screen Framework.

All SAP objects related to this framework can be found in package BUS_TOOLS. This package also contains a small demo transaction, but I think it's a little unclear.

The following steps describe the basis for a screen implementation using BUS-Screen Framework:

- Create a new report with a normal screen. (I've named my screen '2000').

In the Flow Logic of Screen 2000, call modules dynpro_pbo for output, respectively dynpro_pai for input.

PROCESS BEFORE OUTPUT.

     MODULE dynpro_pbo.

PROCESS AFTER INPUT.

     MODULE dynpro_pai.

- Declare these two modules either directly in the report or inside an include.

MODULE dynpro_pbo OUTPUT.

     cl_bus_abstract_screen=>dynpro_pbo(

          iv_dynpro_number    = sy-dynnr

          iv_program_name     = sy-repid ).

ENDMODULE.

MODULE dynpro_pai INPUT.

     cl_bus_abstract_screen=>dynpro_pai(

          iv_dynpro_number    = sy-dynnr

          iv_program_name     = sy-repid ).

ENDMODULE.

NOTE: These modules must only be declared once and then reused for every screen (both normal and sub screens).

- One of the conditions for instantiating screens using this framework is to declare a form routine inside the program.

FORM bus_screen_create USING value(im_program_name) TYPE bus_screen-program_name

                                                       value(im_dynpro_number) TYPE bus_screen-dynpro_number

                                           CHANGING ch_screen ##called.

     CASE im_dynpro_number.

          WHEN '2000'.

" This is the name of the wrapper class for Screen 2000

" If the called iv_dynpro_number is not found and the ch_screen is not instantiated,

" a dummy screen of type CL_BUS_ABSTRACT_SCREEN will be return.

               CREATE OBJECT ch_screen TYPE lcl_demo_main_screen

                    EXPORTING

                         iv_program_name  = im_program_name

                         iv_dynpro_number = im_dynpro_number.

     ENDCASE.

ENDFORM.

- Now it's time to define the screen logic in an object-oriented way using a local ABAP class.

NOTE: Although class CL_BUS_ABSTRACT_SCREEN is the base, it is important to implement the correct inheritance. In this case, CL_BUS_ABSTRACT_MAIN_SCREEN must be used since 2000 is a normal screen. (For sub screens, the corresponding CL_BUS_ABSTRACT_SUB_SCREEN should be used)

CLASS lcl_demo_main_screen DEFINITION

             INHERITING FROM cl_bus_abstract_main_screen

             FINAL.

     PUBLIC SECTION.

" The constructor method can be used for initializations.

          METHODS constructor

               IMPORTING

                    value(iv_program_name) TYPE bus_screen-program_name

                    value(iv_dynpro_number) TYPE bus_screen-dynpro_number.

     PROTECTED SECTION.

" The following two methods must be redefined as ABAP Objects

" does not support the CALL SCREEN statement.

          METHODS call_screen REDEFINITION.

          METHODS call_screen_starting_at REDEFINITION.

     PRIVATE SECTION.

" This method is the central handling for all PAI events in this screen.

          METHODS handle_pai FOR EVENT process_after_input OF cl_bus_abstract_main_screen

                                                IMPORTING iv_function_code.

ENDCLASS.

CLASS lcl_demo_main_screen IMPLEMENTATION.

     METHOD constructor.

          super->constructor(

               EXPORTING

                    iv_program_name = iv_program_name

                    iv_dynpro_number = iv_dynpro_number ).

" The GUI Title of the application is set using the following method

          set_title( 'DEMO BUS-Screen Framework' ).

          SET HANDLER handle_pai FOR me.

     ENDMETHOD.

     METHOD call_screen.

          CALL SCREEN iv_dynpro_number.

     ENDMETHOD.

     METHOD call_screen_starting_at.

          CALL SCREEN iv_dynpro_number

                                   STARTING AT iv_xstart iv_ystart

                                       ENDING AT iv_xend iv_yend.

     ENDMETHOD.

     METHOD handle_pai.

          CASE iv_function_code.

" For the default GUI Status, global constants can be used to evaluate the function code.

" However, if you set your own GUI Status using method set_status( ),

" then you will have to evaluate your specific function codes.

               WHEN gc_function_code_back

                    OR gc_function_code_exit.

                         leave( ).

               WHEN gc_function_code_cancel.

                         LEAVE PROGRAM.

          ENDCASE.

     ENDMETHOD.

ENDCLASS.

- Now that our screen is defined, we can call it. For this, the following code should be used in the START-OF-SELECTION event:

DATA lo_main_screen TYPE REF TO lcl_demo_main_screen.

" This statement will try to call the BUS_SCREEN_CREATE form routine that we previously defined.

cl_bus_abstract_screen=>get_screen(

     EXPORTING iv_program_name = sy-repid

                           iv_dynpro_number = '2000'

     IMPORTING ev_screen = lo_main_screen ).

IF lo_main_screen IS BOUND.

     lo_main_screen->show( ).

ENDIF.

This pretty much sums up the basic functionality. In the next blogs, I will show you how to use the tabstrip wrapper (CL_BUS_TABSTRIP and CL_BUS_TABSTRIP_TAB classes) and also how to handle messages (CL_BUS_MESSAGE).