WD - URL Parameters and Application Parameters

SAP help on this point:

http://help.sap.com/saphelp_nw70/helpdata/en/7b/fb57412df8091de10000000a155106/content.htm

 

To read the URL parameters, we need below codes in the HANDLEDEFAULT method of a window.
of the default window controller

 

DATA : it_parameter TYPE tihttpnvp,
             wa_parameter  TYPE ihttpnvp.
 
  " Get all URL parameters
  CALL METHOD wdevent->get_data
    EXPORTING
      name  = if_wd_application=>all_url_parameters
    IMPORTING
      value = it_parameter.
 
  " Get parameter values
  CLEAR wa_parameter.
  READ TABLE it_parameter WITH KEY name = 'PERNR' INTO wa_parameter.
  IF sy-subrc EQ 0.
    ls_url_param-pernr = wa_parameter-value.
  ENDIF. 

 

Somehow below codes can NOT work in my side.

  DATA: lo_fpm TYPE REF TO if_fpm,
        lo_params TYPE REF TO if_fpm_parameter,
        l_view_name TYPE string.
  lo_fpm = cl_fpm_factory=>get_instance( ).
  lo_params = lo_fpm->mo_app_parameter.
  IF lo_params IS NOT INITIAL.
    lo_params->get_value(
      EXPORTING iv_key   = 'viewname'       "Application param name
      IMPORTING ev_value = l_view_name ).
    IF l_view_name = 'VH'.
      wd_this->fire_dispreqhistory_plg( ).
    ENDIF.
  ENDIF.