quit an embedded viz-simulation

[levisii]

oh, i'm sorry. first time i'm posting here
i've splitted my code to one files per class, but if you run this, it is showing my problem:

import viz, wx

#This class implements the GUI-Frame
class MainFrame(wx.Frame):
    def __init__(self, parent, id, title):
        wx.Frame.__init__(self, parent, id, title)

        #Menubar
        menubar 	= wx.MenuBar()
        worldViz 	= wx.Menu()
        worldViz.Append(104, '&Simulation', 'Start a 3D-simulation')
        menubar.Append(worldViz, '&WorldViz')
        self.SetMenuBar(menubar)
        self.CreateStatusBar()

        wx.EVT_MENU(self, 104, self.onStart3D)

    #calls the embedded simulation
    def onStart3D(self, event):
        self.timer = wx.Timer(self, 5000)   #Timer for updating the frames
        self.timer.Start(10)
        wx.EVT_TIMER(self, 5000, self.onTimer)

        viz.go(viz.EMBEDDED)
        simulation()

    #Manuel FrameUpdate
    def onTimer(self, event):
        viz.updateframe()
        
#this is my test simulation
def simulation():
    viz.clearcolor(0.5, 0.5, 1.0)

    #Set ViewPoint
    view = viz.MainView
    view.setPosition(0, 1, -20)

    #Turn on the physics engine
    viz.phys.enable()

    #Add ground
    ground = viz.add('tut_ground.wrl')
    ground.collidePlane()

#Exit-function
def onkeydown(key):
    if key == '1':
        print 'onKeyDown() executed'
        viz.quit()

viz.callback(viz.KEYDOWN_EVENT, onkeydown)

def onexit():
    print'onExit() executed'
    viz.quit()

viz.callback(viz.EXIT_EVENT, onexit)


#this is the starting class
class MainApp(wx.App):
	def OnInit(self):
		frame = MainFrame(None,-1, 'Phantom')
		frame.Show(True)
		return True

app = MainApp(0)
app.MainLoop()
del app