How implement a "back" key? when I have two level of windows?

[ftp2012]

Thanks for bogdan.galiceanu's help,now I have a skeleton of UI.
but I have a further question, as the following codes, I have a initial window "Listbox",and the second window "Canvas". The "Canvas" shows the realtime data. I want to implement a "back" not "quit" key on the canvas' right softkey.
How to do ?
Thanks

#-*- coding: UTF-8 -*- 
import appuifw
import time
# import graphics
from graphics import *
def quit():
     running = 0
     t.cancel()
     app_lock.signal()
# define a callback function
def shout():
    index = lb.current()
    if index ==0:
        global img,canvas,mytimer
        canvas=appuifw.Canvas(event_callback=None, redraw_callback=handle_redraw)
        appuifw.app.directional_pad = False
        # define an initial image (white)
        img=Image.new(canvas.size)
        img.text((100,80), u'')
        update_data()
    if index == 1:
        pass
    if index ==2:
       pass
    if index ==3:
        pass
# define your redraw function (that redraws the picture on and on)
# in this case we redraw the image named img using the blit function
def handle_redraw(rect):
    img.clear()
    img.line((20,20,20,120),0xff00ee)
    img.text((100,80), str1,fill = 0x0,font='normal')
    canvas.blit(img)
flag = 1
str1 = ''
def  update_data():
    global flag,str1
    if flag == 1:
        str1 = u'good'
        flag =0
    else:
        str1 = u'bad'
        flag =1
    handle_redraw(())
    t.after(10,update_data)
if __name__ == "__main__":
    import e32
    app_lock =e32.Ao_lock()
    appuifw.app.exit_key_handler = quit
    t = e32.Ao_timer()
    appuifw.app.title = u'Listbox_canvas'
    # create your content list of your listbox including the icons to be used for each entry
    entries = [u'canvas_test',u'item1',u'item2',u'item3']
    lb = appuifw.Listbox(entries,shout)
    # create an instance of appuifw.Listbox(), include the content list "entries" and the callback function "shout"
    # and set the instance of Listbox now as the application body
    appuifw.app.body = lb
    app_lock.wait()

[bogdan.galiceanu]

You might find this thread useful: http://discussion.forum.nokia.com/fo...esign-in-PyS60 (see especially post #2 and #5).

The idea is that you memorize the UI elements of your first window, switch to the second window, and assign a function to the right softkey. This function simply replaces the elements of the current window with those from the first window, which you memorized.

[ftp2012]

so clear implemtention!
sharing my testing codes as following:

#-*- coding: UTF-8 -*- 
import appuifw
import time
# import graphics
from graphics import *
def quit():
     app_lock.signal()
# define a callback function
def shout():
    index = lb.current()
    if index ==0:
        global img,canvas,mytimer
        canvas=appuifw.Canvas(event_callback=None, redraw_callback=handle_redraw)
        appuifw.app.directional_pad = False
        viewStack.append(canvas)
        show()
        appuifw.app.exit_key_handler = back
        # define an initial image (white)
        img=Image.new(canvas.size)
        img.text((100,80), u'')
        update_data()
    if index == 1:
        pass
    if index ==2:
       pass
    if index ==3:
        pass
# define your redraw function (that redraws the picture on and on)
# in this case we redraw the image named img using the blit function
def handle_redraw(rect):
    img.clear()
    img.line((20,20,20,120),0xff00ee)
    img.text((100,80), str1,fill = 0x0,font='normal')
    canvas.blit(img)
flag = 1
str1 = ''
def  update_data():
    global flag,str1
    if flag == 1:
        str1 = u'good'
        flag =0
    else:
        str1 = u'bad'
        flag =1
    handle_redraw(())
    t.after(10,update_data)
def show():
    if len(viewStack) > 0:
        appuifw.app.body = viewStack[-1]

def back():
    t.cancel()
    if len(viewStack) -1 > 0:
        viewStack.pop()
        show()
if __name__ == "__main__":
    import e32
    app_lock =e32.Ao_lock()
    viewStack =[]
    appuifw.app.exit_key_handler = quit
    t = e32.Ao_timer()
    appuifw.app.title = u'Listbox_canvas'
    # create your content list of your listbox including the icons to be used for each entry
    entries = [u'canvas_test',u'item1',u'item2',u'item3']
    lb = appuifw.Listbox(entries,shout)
    # create an instance of appuifw.Listbox(), include the content list "entries" and the callback function "shout"
    # and set the instance of Listbox now as the application body
    viewStack.append(lb)
    show()
    app_lock.wait()

You might find this thread useful: http://discussion.forum.nokia.com/fo...esign-in-PyS60 (see especially post #2 and #5).

The idea is that you memorize the UI elements of your first window, switch to the second window, and assign a function to the right softkey. This function simply replaces the elements of the current window with those from the first window, which you memorized.

[Rafael T.]

Thanks for bogdan.galiceanu's help,now I have a skeleton of UI.
but I have a further question, as the following codes, I have a initial window "Listbox",and the second window "Canvas". The "Canvas" shows the realtime data. I want to implement a "back" not "quit" key on the canvas' right softkey.
How to do ?
Thanks

You can do something like:

def back():
    appuifw.app.body = lb

appuifw.app.exit_key_handler = back

Just a easier reference for those who will look for this later