Multi level tree ALV with CL_GUI_LIST_TREE

DATA : lr_cust TYPE REF TO cl_gui_custom_container,
lr_list_tree TYPE REF TO cl_gui_list_tree,
lt_flight TYPE TABLE OF scarr,
ls_flight TYPE scarr,
lt_spfli TYPE TABLE OF spfli,
ls_spfli TYPE spfli,
lt_node TYPE treev_ntab,
ls_node TYPE LINE OF treev_ntab,
lt_item TYPE TABLE OF mtreeitm,
ls_item TYPE mtreeitm .

START-OF-SELECTION.
CALL SCREEN 0001.
*&———————————————————————*
*&      Module  STATUS_0001  OUTPUT
*&———————————————————————*
MODULE status_0001 OUTPUT.
SET PF-STATUS ‘LIST_STATUS’.
ENDMODULE.                 ” STATUS_0001  OUTPUT
*&———————————————————————*
*&      Module  GET_DATA  OUTPUT
*&———————————————————————*
MODULE get_data OUTPUT.
IF lt_flight IS INITIAL.
SELECT * FROM scarr INTO TABLE lt_flight.
IF lt_flight IS NOT INITIAL.
SELECT * FROM spfli INTO TABLE lt_spfli FOR ALL ENTRIES IN lt_flight
WHERE carrid = lt_flight–carrid.
ENDIF.
ENDIF.
ENDMODULE.                 ” GET_DATA  OUTPUT
*&———————————————————————*
*&      Module  BUILD_LIST_TREE  OUTPUT
*&———————————————————————*
MODULE build_list_tree OUTPUT.
IF lr_cust IS NOT BOUND.
CREATE OBJECT lr_cust
EXPORTING
container_name = ‘LIST_TREE’
repid          = sy–repid
dynnr          = sy–dynnr.
ENDIF.

IF lr_list_tree IS NOT BOUND.
CREATE OBJECT lr_list_tree
EXPORTING
parent                      = lr_cust
node_selection_mode         = cl_gui_list_tree=>node_sel_mode_single
*       hide_selection              =     ” Visibility of Selection
item_selection              = ‘X’  ” Can Individual Items be Selected?
with_headers                = ‘ ‘    ” ‘X’: With Headers
*       hierarchy_header            =     ” Hierarchy Header
*       list_header                 =     ” List Header
*       name                        =     ” Name
EXCEPTIONS
lifetime_error              = 1
cntl_system_error           = 2
create_error                = 3
illegal_node_selection_mode = 4
failed                      = 5
OTHERS                      = 6.
ENDIF.

IF lr_list_tree IS BOUND.
* Building Root Node
ls_node–node_key = ‘Flight’.
ls_node–hidden = ‘ ‘.
ls_node–hidden = ‘ ‘.
ls_node–isfolder = ‘X’.
APPEND ls_node TO lt_node.
* Building sub node and relationship with root node
LOOP AT  lt_flight INTO ls_flight.
ls_node–node_key = ls_flight–carrid.
ls_node–relatkey = ‘Flight’.
ls_node–relatship = cl_gui_list_tree=>relat_last_child.
ls_node–isfolder = ‘X’.
APPEND ls_node TO lt_node.
LOOP AT lt_spfli INTO ls_spfli WHERE carrid = ls_flight–carrid.
ls_node–node_key = ls_spfli–connid.
ls_node–relatkey = ls_flight–carrid.
ls_node–relatship = cl_gui_list_tree=>relat_last_child.
ls_node–isfolder = ‘X’.
APPEND ls_node TO lt_node.
ENDLOOP.
ENDLOOP.
* Building root Node Text
ls_item–node_key = ‘Flight’.
ls_item–item_name = ‘1’.
ls_item–class = cl_gui_list_tree=>item_class_text.
ls_item–alignment = cl_gui_list_tree=>align_auto.
ls_item–font = cl_gui_list_tree=>item_font_prop.
ls_item–text = ‘Flight_Info’.
APPEND ls_item TO lt_item.
* Bulding all Item node text
LOOP AT  lt_flight INTO ls_flight.
ls_item–node_key = ls_flight–carrid.
ls_item–item_name = ‘1’.
ls_item–class = cl_gui_list_tree=>item_class_text.
ls_item–alignment = cl_gui_list_tree=>align_auto.
ls_item–font = cl_gui_list_tree=>item_font_prop.
ls_item–text = ls_flight–carrname.
APPEND ls_item TO lt_item.
LOOP AT lt_spfli INTO ls_spfli WHERE carrid = ls_flight–carrid.
ls_item–node_key = ls_spfli–connid.
ls_item–item_name = ‘1’.
ls_item–class = cl_gui_list_tree=>item_class_text.
ls_item–alignment = cl_gui_list_tree=>align_auto.
ls_item–font = cl_gui_list_tree=>item_font_prop.
CONCATENATE ls_spfli–countryfr ‘-‘ ls_spfli–cityfrom ‘-‘
ls_spfli–countryto ‘-‘ ls_spfli–cityto INTO ls_item–text.

APPEND ls_item TO lt_item.

ENDLOOP.
ENDLOOP.

CALL METHOD lr_list_tree->add_nodes_and_items
EXPORTING
node_table                     = lt_node
item_table                     = lt_item
item_table_structure_name      = ‘MTREEITM’
EXCEPTIONS
failed                         = 1
cntl_system_error              = 2
error_in_tables                = 3
dp_error                       = 4
table_structure_name_not_found = 5
OTHERS                         = 6.

ENDIF.
ENDMODULE.                 ” BUILD_LIST_TREE  OUTPUT
*&———————————————————————*
*&      Module  USER_COMMAND_0001  INPUT
*&———————————————————————*
*       text
*———————————————————————-*
MODULE user_command_0001 INPUT.
CASE sy–ucomm.
WHEN ‘BACK’ OR ‘EXIT’ OR ‘CANCEL’.
LEAVE TO SCREEN 0.
ENDCASE.
ENDMODULE.                 ” USER_COMMAND_0001  INPUT