ALV with dropdown in column and other questions

Question

hi,
I created an editable alv with configuration model via external context mapping.
now I have a column which contains strings and my aim is to show this whole column as a dropdownlist. the possible values of this dropdown are fetched in a database table at  runtime and each cell in this column got its own selected value in this dropdownlist.
changes of the selected values should be written in the database table in a later step.
1. what changes do I have to do?
should I remove my external mapping concerning the alv and use the setData method? or what is the easiest way to get my dropdownlist in this column instead of normal text (string) ?
2. should I choose dropdownbykey or by index?
   I suppose I have to change the context when changing the selected value in the dropdownlist and the read out the changed context element and update my database table?
3. how could I access rows (= tuples) in an alv?
4. how can I avoid that a row could be deleted, inserted or added with the normal functions of the alv?

Answer 1

Hi Thorsten,
If the possible list of values in the dropdown is different for each row, you need a drop down by index. Else this can be done using a dropdown by key itself.
The only change that you need to do is create a cell editor of type dropdown for that particular column and configure your ALV model.
The sample code for changing the cell editor would be:
    l_alv_model = l_ref_interfacecontroller->get_model( ).
  DATA:
     lr_column_settings TYPE REF TO if_salv_wd_column_settings,
     lr_column type ref to CL_SALV_WD_COLUMN.
     lr_dropdown TYPE REF TO CL_SALV_WD_UIE_DROPDOWN_BY_KEY.
  lr_column_settings ?= l_alv_model.
  lr_column = lr_column_settings->get_column( <column name> ).
  CREATE OBJECT lr_dropdown EXPORTING 
  SELECTED_KEY_FIELDNAME= '<fieldname>'
  lr_column->set_cell_editor( lr_dropdown ).
Here, you can substitute the field name with your field name that has to be displayed as a dropdown.
The dropdown list can be populated in the wddoinit method by attaching a value set to the attribute in the context node info. Everything else will be like you do in a normal table. You can so a get_static_attributes of your elements and persist in tables. Whenever you change the selected value, the context will be updated immediately. You can have a user defined function like 'Save' or something where you can just read the context and process the data.
If you do not want to display any of the normal functions, you can do the following:
data: lt_functions type SALV_WD_T_FUNCTION_STD_REF,
        ls_function type SALV_WD_s_FUNCTION_STD_REF.
lt_functions = l_alv_model->if_salv_wd_function_settings~get_functions_std( ).
loop at lt_functions into ls_function.
ls_function-r_function->set_visible( CL_WD_UIELEMENT=>E_VISIBLE-NONE ).
endloop.
The above code will hide all the standard functions. If you want to hide specific ones, do a get_function(id) and set_visible.
Hope this helps.
Regards
Nithya