Python unity indicator applet and glade child window exits at the same time

Question

Since I don't have much reputation. The original question has been posted in stackoverflow and here is the link:
Python unity indicator applet and glade child window

I have created an unity indicator applet with python and glade. Here is the screenshot that appears when indicator applet is clicked. You can see the preferences menu. When this preferences menu is clicked, it opens a new window.

Indicator Applet Menu

Preference Window

Now the problem is when I click on close button, the whole application exists.

The code that triggers the preference window is as shown below :

def action_preferences(self, widget):
    '''
    Show the preferences window
    '''
    base = PreferenceWindow()
    base.main()

    self.menu_setup()

preference.py has the following code :

import sys
import json
import pynotify

try:
    import pygtk
    pygtk.require("2.0")
except:
    pass
try:
    import gtk
    import gtk.glade
except:
    print("GTK is not Available")
    sys.exit(1)

class PreferenceWindow:
    ui = None
    configs = {}
    notify = None
    window = None

    def __init__(self):

        if not pynotify.init ("nepal-loadshedding"):
            sys.exit (1)

        self.ui = gtk.glade.XML("pref_ui.glade")

        # Get the preference saved previously
        self.configs = self.parse_configs()

        saved_group_value = str(self.configs.get("GROUP"))

        self.ui.get_widget("text_group_number").set_text(saved_group_value)

        dic = {
            "on_btn_pref_ok_clicked":self.on_save_preference,
            "on_btn_pref_close_clicked":self.on_close,
            "on_preference_window_destroy":self.on_quit,
            }

        self.ui.signal_autoconnect(dic)

        if self.window is None:               
            self.window = self.main()

    def parse_configs(self):
        self.configs = json.load(open("config.txt"))
        return self.configs

    def save_configs(self, key, value):
        self.configs[key] = int(value)
        json.dump(self.configs, open("config.txt", "wb"))
        return True

    def on_save_preference(self, widget):
        group_number = self.ui.get_widget("text_group_number").get_text()
        self.save_configs("GROUP", group_number)

        # try the icon-summary case
        if self.notify == None:
            self.notify = pynotify.Notification ("Nepal Loadshedding", "Group saved successfully to : " + group_number)
        else:
            self.notify.update("Nepal Loadshedding", "Group saved successfully to : " + group_number)
            self.notify.set_timeout(100)

        self.notify.show()
        print "Saved successfully"

    def on_close(self, widget):
        print 'close event called'

    def on_quit(self, widget):
        sys.exit(0)

    def main(self):
        gtk.main()

Answer 1

            "on_preference_window_destroy":self.on_quit,

This line is your problem. When the window is destroyed, you're calling a quit method. When you close the window, it gets destroyed, thus resulting in your quit method being called.

Also, you don't want to call sys.exit(0) to exit a GTK+ application. You want to use Gtk.main_quit() instead. It would also be a good idea to convert your application to using the gobject-introspection bindings for GTK+ and related libraries, rather than using the old and deprecated pygtk bindings.