Key event down

i cannot do work key down event pls give me a hand thanks this is my
code:

require “rubygems”
require “wx”
include Wx

class MyFrame < Frame

def initialize
super(nil, #Parent
:title => “RadioBox Example”, #Displays on top of window
:pos => [1030, 25], #or Wx::DEFAULT_POSITION
:size => [250, 500] #or Wx::DEFAULT_SIZE

      #For the position and size arguments, you don't need to 

specify Point and Size
#objects anymore. See: wxRuby Overview on the doc page
wxruby_intro.html
)
evt_key_down() { | ev | @text_position.label = “working key down” }

panel = Wx::Panel.new(self)    #Parent = self = this Frame

drink_choices = ["coffee", "tea", "juice", "milk"]   #labels for 

radio buttons

radios = Wx::RadioBox.new(
    panel,                        #Parent
    :label => "Drinks",           #Label for box surrounding radio 

buttons
:pos => [20, 5],
:size => Wx::DEFAULT_SIZE,
:choices => drink_choices, #The labels for the radio buttons
:major_dimension => 1, #Max number of columns(see next
line)–try changing it to 2
:style => Wx::RA_SPECIFY_COLS #:major_dimension value applies to
columns

    #The :major_dimension and :style in combination determine the 

layout of the
#RadioBox. In this case, the maximum number of columns is 1,
which means
#there can only be one radio button per line. Because there are
4 radio buttons,
#that means there will be 4 lines, with one radio button per
line.

)
evt_radiobox(radios.get_id()) {|cmd_event| 

on_change_radio(cmd_event)}

@text_widget = Wx::StaticText.new(
    panel,                  #Parent
    :label => "coffee",
    :pos => [150, 25],
    :size => Wx::DEFAULT_SIZE

    #Store a widget in an instance variable when other
    #methods, like the one below, need access to it.
)

boton = Wx::Button.new(
  panel,
  :label => "Posicion",
  :pos => [20,120],
  :size => Wx::DEFAULT_SIZE,
  :style => 0,
  :validator => Wx::DEFAULT_VALIDATOR,
  :name => "button"

  )
evt_button(boton) {|cmd_event| on_click(cmd_event)}

 @text_position = Wx::StaticText.new(
    panel,                  #Parent
    :label => "Position",
    :pos => [150, 120],
    :size => Wx::DEFAULT_SIZE

    #Store a widget in an instance variable when other
    #methods, like the one below, need access to it.
)



#When there is an event of type evt_radiobox on the widget with the 

id radios.get_id(),
#the block is called and an “event object” is passed to the block.
The block calls
#the method on_change_radio(), defined below, relaying the event
object to the
#method. The event object contains useful information about the
radio button
#that was selected.

show     #equivalent to self.show, makes the frame visible

end

def on_change_radio(cmd_event)
selected_drink = cmd_event.string #Selected radio’s label

#Instead of calling cmd_event.get_string() or 

cmd_event.set_string(), you can
#now call an accessor method with the same name as the property you
are trying
#to get or set. See: wxRuby Overview on the doc page
wxruby_intro.html

@text_widget.label = selected_drink

end
def on_click(cmd_event)

 @text_position.label = "testeando"

end

end

class MinimalApp < Wx::App
def on_init
MyFrame.new
end
end

MinimalApp.new.main_loop #main_loop() tells wxruby to start reacting
#to radio button selections, button clicks,
etc.
#on your App.