ALV – ABAP List Viewer Programming (Lesson - 11)

The common desired  features of any  report are “column alignment”, sorting, filtering, subtotals, totals etc. To implement these from scratch , a lot of coding effort  is to be put. To avoid that we can use a concept called ABAP List Viewer (ALV).
Using ALV, we can have three types of reports:

1. Simple Report
2. Block Report
3. Hierarchical Sequential Report

Each of these reports provide function modules which help in producing desired output without much effort. Lets look at them in detail -

Simple Report

Important function modules in these report are -

• Reuse_alv_fieldcatalog_merge
• Reuse_alv_list_display
• Reuse_alv_events_get
• Reuse_alv_grid_display
• Reuse_alv_commentary_write

REUSE_ALV_FIELDCATALOG_MERGE
This function module is used to populate a field catalog which is essential to display the data in ALV.
If the output data is from a single dictionary table and all the columns are selected, then we need not exclusively create the field catalog. Its enough to mention the table name as a parameter (I_structure_name) in the REUSE_ALV_LIST_DISPLAY. But in other cases we need to create it.
Note : Fieldcatalog can be filled manually also by filling up all the required details into the internal table
Important parameters in are:
1. Export:

• I_program_name : report id
• I_internal_tabname : the internal output table
• I_inclname : include or the report name where all the dynamic forms are handled.

2. Changing

• ct_fieldcat : an internal table with the type SLIS_T_FIELDCAT_ALV which is declared in the type pool SLIS.

REUSE_ALV_LIST_DISPLAY
This is the function module which prints the data.
The important parameters are:
1. Export:

• I_callback_program : report id
• I_bypassing_buffer : ‘X’
• I_buffer_active : ‘ ‘
• I_callback_pf_status_set : routine where a user can set his own pf status or change the functionality of the existing pf status.
• I_callback_user_command : routine where the function codes are handled.

• I_structure name : name of the dictionary table
• Is_Layout : structure to set the layout of the report
• It_fieldcat : internal table with the list of all fields and their attributes which are to be printed (this table can be populated automatically by the function)
• It_events : internal table with a list of all possible events of ALV and their corresponding form names.

2. Tables:

• a. t_outtab : internal table with the data to be output

REUSE_ALV_EVENTS_GET:
Returns table of possible events for a a list type
1. Import:
Et_Events :The event table is returned with all possible CALLBACK events for the specified list type (column ‘NAME’). For events to be processed by the Callback, their ‘FORM’ field must be filled. If the field is initialized, the event is ignored. The entry can be read from the event table, the field ‘FORM’ filled and the entry modified using constants from the type pool SLIS.
2. Export:
I_list_type: 0 = simple list REUSE_ALV_LIST_DISPLAY
1 = hierarchical-sequential list  REUSE_ALV_HIERSEQ_LIST_DISPLAY
2 = simple block list REUSE_ALV_BLOCK_LIST_APPEND
3 = hierarchical-sequential block list   REUSE_ALV_BLOCK_LIST_HS_APPEND
REUSE_ALV_GRID_DISPLAY
A new function from ABAP4.6 version, to display the results in grid rather than a preview.
Parameters : same as reuse_alv_list_display

Note:Grid cannot handle high volumes. Functions like sort, scrolling down consumes a lot of resources / time if the volume of data to be displayed is high. There is no clear cut definition such that if the amount of data is X go for list or grid  but the developer has to take a call based on his experience. If not sure, then list is the better option

REUSE_ALV_COMMENTARY_WRITE
This is used in the Top-of-page event to print the headings and other comments for the list.
Important Parameters

• It_list_commentary : Internal table with the headings of the type slis_t_listheader.

This internal table has three fields:

1. Typ : ‘H’ – header, ‘S’ – selection, ‘A’ – action
2. Key : only when typ is ‘S’.
3. Info : the text to be printed

Block Report

This looks like a simple report but this report has the features of sorting and filtering only.This report is used if you have to display more than one report on the output. Technically speaking if you have multiple internal table with data to be displayed as separate blocks then we go for block report of ALV.
The important functions used for creating this report are:

• REUSE_ALV_BLOCK_LIST_INIT
• REUSE_ALV_BLOCK_LIST_APPEND
• REUSE_ALV_BLOCK_LIST_DISPLAY

REUSE_ALV_BLOCK_LIST_INIT
This function module is used to set the default gui status etc. The parameters are similar to the one used in reuse_alv_list_display or reuse_alv_grid_display
REUSE_ALV_BLOCK_LIST_APPEND
This function module adds the data to the block.
Important Parameters
1.Export :

• is_layout : layout settings for block
• it_fieldcat : field catalog
• I_tabname : internal table name with all all possible events

2.Tables :

• t_outtab : internal table with output data.

REUSE_ALV_BLOCK_LIST_DISPLAY
This function module display the list with data appended by the above function.
Parameters : All the parameters are optional.

Hierarchical Reports

Hierarchical display is used for displaying data that are related. Like sales order and item details. Here sales order details can be the header data whereas them items in the sales order can be the item data
The function module used for this is
REUSE_ALV_HIERSEQ_LIST_DISPLAY
Export:

• I_CALLBACK_PROGRAM
• I_CALLBACK_PF_STATUS_SET
• I_CALLBACK_USER_COMMAND
• IS_LAYOUT
• It_fieldcat
• It_events
• I_tabname_header : Name of the internal table in the program containing the output data of the highest hierarchy level.
• I_tabname_item : Name of the internal table in the program containing the output data of the lowest hierarchy level.
• Is_keyinfo : This structure contains the header and item table field names which link the two tables (shared key).

Tables

• t_outtab_header : Header table with data to be output
• t_outtab_item : Name of the internal table in the program containing the output data of the lowest hierarchy level.

All the definitions of internal tables, structures and constants are declared in a type-pool called SLIS. This internal table can be populated automatically by using REUSE_ALV_FIELDCATALOG_MERGE’.

Display Variants

• Display variants are used to set the default properties of an alv output like sort criteria, filtering criteria, totaling and subtotaling etc
• Display variants can be user specific and standard (standard variants can be used by any user )
• Kind of display variants that can be saved is controlled by the parameter i_save that is passed in function modules  reuse_alv_list_display / reuse_alv_grid_display
• You can provide an option on the selection screen to select what display variant to be used

The common function modules related to selecting / validating display variants are

1. Reuse_alv_variant_default_get
2. Reuse_alv_variant_f4
3. Reuse_alv_variant_existence

Thats all to ABAP- ALV programming!