Description

Question

AT SELECTION SCREEN OUTPUT
AT SELECTION-SCREEN ON VALUE-REQUEST
AT SELECTION-SCREEN ON HELP-REQUEST
AT SELECTION-SCREEN ON
AT SELECTION-SCREEN ON BLOCK
AT SELECTION-SCREEN ON RADIOBUTTON GROUP
can any one explain these events in detail and when they will trigger .Its urgent please

Answer 1

Hi,
EVENTS in ABAP Report
These are the Events(In order of execution) in ABAP Report
1.INITIALIZATION
2.AT SELECTION SCREEN OUTPUT
3.AT SELECTION-SCREEN ON VALUE-REQUEST
4.AT SELECTION-SCREEN ON HELP-REQUEST
5.AT SELECTION-SCREEN ON
6.AT SELECTION-SCREEN ON BLOCK
7.AT SELECTION-SCREEN ON RADIOBUTTON GROUP
8.AT SELECTION-SCREEN
Selection screen processing starts after the INITIALIZATION event with AT SELECTION SCREEN OUTPUT. The selection screen is then sent to the screen. User actions on the selection screen result in other events that are either used for field or possible entries help, or that trigger PAI processing of the selection screen. During PAI processing, error messages in the relevant event blocks allow users to return to the selection screen. Only if the AT SELECTION-SCREEN event is exited properly, that is not through an error message, are the other events of the executable program triggered, starting with START-OF-SELECTION.
<b>INITIALIZATION</b>
This event occurs before the standard selection screen is called. You can use it, for example, to initialize the input fields of the standard selection screen. This is the only possible way to change the default values of parameters or selection criteria defined in logical databases. To change a selection criterion, you must fill at least the components <seltab>-SIGN,
<seltab>-OPTION, and <seltab>-LOW of the selection table <seltab>, otherwise it remains undefined.
In the PBO of the selection screen, the
<b>AT SELECTION-SCREEN OUTPUT</b>
event is triggered. This event block allows you to modify the selection screen directly before it is displayed.
<b>AT SELECTION-SCREEN ON VALUE-REQUEST FOR <field></b>
The event is triggered when the user calls the F4 help for the field <field>. If no corresponding event block has been defined, the possible values help from the ABAP Dictionary is displayed, or none at all if the field has no Dictionary reference. If a corresponding event block exists, it takes precedence over the default possible values help mechanism. It is then up to the programmer to ensure that an appropriate list of values is displayed, and that the user can choose a value from it.
You cannot declare the event block AT SELECTION-SCREEN ON VALUE-REQUEST for input fields on the selection screen that are declared within a logical database. You cannot override the possible values help mechanism of a logical database within the program. You can define separate help within the logical database program using the VALUE-REQUEST option in the PARAMETERS and SELECT-OPTIONS statements.
<b>AT SELECTION-SCREEN ON HELP-REQUEST FOR <field></b>
The event is triggered when the user calls the F1 help for the field <field>. If no corresponding event block has been defined, the help from the ABAP Dictionary is displayed, or none at all if the field has no Dictionary reference. If a corresponding event block exists, it takes precedence over the default help mechanism. It is then up to the programmer to ensure that appropriate help is displayed.
You cannot declare the event block AT SELECTION-SCREEN ON HELP-REQUEST for input fields on the selection screen that are declared within a logical database. You cannot override the help mechanism of a logical database within the program. You can define separate help within the logical database program using the HELP-REQUEST option in the PARAMETERS and SELECT-OPTIONS statements.
<b>AT SELECTION-SCREEN ON <field></b>
In the PAI event of the selection screen, the event
is triggered when the contents of each individual input field are passed from the selection screen to the ABAP program. The input field <field> can be checked in the corresponding event block. If an error message occurs within this event block, the corresponding field is made ready for input again on the selection screen.
<b>AT SELECTION-SCREEN ON BLOCK <block></b>
In the PAI event of the selection screen, the event
is triggered when the contents of all of the fields in a block are passed from the selection screen to the ABAP program. You define a block by enclosing the declarations of the elements in the block between the statements SELECTION-SCREEN BEGIN OF BLOCK <block> and SELECTION-SCREEN END OF BLOCK <block>. You can use this event block to check the consistency of the input fields in the block. If an error message occurs within this event block, the fields in the block are made ready for input again on the selection screen.
<b>AT SELECTION-SCREEN ON RADIOBUTTON GROUP <radi></b>
In the PAI event of the selection screen, the event
is triggered when the contents of all of the fields in a radio button group are passed from the selection screen to the ABAP program. To define a radio button group <radi>, use the addition RADIOBUTTON GROUP <radi> in the corresponding PARAMETERS statements. This event block allows you to check the whole group. If an error message occurs within this event block, the radio button group is made ready for input again on the selection screen. The individual fields of radio button groups do not trigger the event AT SELECTION-SCREEN ON <field>.
<b>AT SELECTION-SCREEN</b> is the basic form of a whole series of events that occur while the selection screen is being processed.
The standard selection screen in an executable program or in the logical database linked to it is automatically called between the INITIALIZATION and START-OF-SELECTION events. When you call the selection screen, and when users interact with it, the ABAP runtime environment generates selection screen events, which occur between INITIALIZATION and START-OF-SELECTION.
Regards,
Ranjit Thakur.
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