I program some trees in java webdynpro, but in abap wd it’s slightly different…easier on one side, but with no documentation could be quite complex.

Suppose you wish to build a dynamic tree, so you declare a tree control with a recursive node under it:

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The tree node type shoud be binded to a context node which contain a recursive node under it; in this case the treeservices is the upper node of the tree in the context.

 the event ‘onLoadChildren’ is raised when you expand a tree node; here the critical role is assumed by the parameter PATH which tell us positioning.

Here, the method ZGETLEAF of the component controller will retrieve the data for the expanded node:

method ZGETLEAF .   DATA ls_treeservices TYPE wd_this->Element_treeservices.   data: treeserv type table of wd_this->element_treeservices.   data valore type char10.   data tabhier type table of zzservhier.   data shier type zzservhier.   data nodo type ref to if_wd_context_node.   data myset type WDR_CONTEXT_ELEMENT_SET.   data valflag.   data cxcontext type ref to cx_wd_context.   data prestazione type char10.   data prestaziones type string.   data resto type string.   data espanso type flag.   data nodes type WDR_CONTEXT_CHILD_MAP.   data snodes type WDR_CONTEXT_CHILD.   data nodeinfo type ref to IF_WD_CONTEXT_NODE_INFO.   data nodename type string.   data indice type i.   data loaded type flag.     indice = parent->get_index( ).   nodo = node->get_child_node( index = indice  name = ‘TREELEAF’ ).       call method parent->get_attribute         exporting            name = ‘EXPANDED’         importing            value = espanso.      check espanso = ‘X’.      call method parent->get_attribute        exporting           name = ‘LOADED’        importing          value = loaded.     check loaded = space.       call method parent->get_attribute         exporting            name = ‘CODICE’         importing            value = prestaziones.       split prestaziones at ‘-‘ into prestazione resto.      call method parent->set_attribute          exporting             name = ‘LOADED’             value = ‘X’.      CALL FUNCTION ‘ZZ_GET_CORDER_HIERARCHY’         EXPORTING           I_TALST         = prestazione           LEVEL           = ’01’         TABLES           HIERARCHY       = tabhier                 .       loop at tabhier into shier. *          concatenate shier-prestazione ‘-‘ *                      shier-descrizione into prestaziones.           prestaziones = shier-prestazione.           ls_treeservices-codice = prestaziones.           ls_treeservices-nome   = shier-descrizione.           ls_treeservices-figli = shier-cartella.           append ls_treeservices to treeserv.       endloop.      nodo->bind_table(     new_items             =  treeserv     set_initial_elements = abap_false ).  endmethod.

Of course, I use an attribute in the tree context to know if I already loaded the data for that branch.

Also the first level of the tree is loaded in the WDDOINIT method of the view(via calling of a component controller method).