Is it possible to schedule Kivy StringProperty set() method using Clock? - string

Question

I would like to delay Kivy screen manager transition, which I can do for example like this:
#!/usr/bin/env python
from kivy.app import App
from kivy.lang import Builder
from kivy.uix.floatlayout import FloatLayout
from kivy.properties import StringProperty
from kivy.uix.button import Button
from kivy.clock import Clock
Builder.load_string('''
#: kivy 1.9.2
#: import sm kivy.uix.screenmanager
#: set base_font_size 25
<MainWidget>:
manager: screen_manager
ScreenManager:
id: screen_manager
transition: sm.NoTransition()
Screen:
name: 'screen_one'
Button:
text: 'Screen 1, press to switch to Screen 2'
font_size: base_font_size
on_press:
root.manager.current = 'screen_two'
root.statusmsg = 'Screen 2, press to launch Armageddon'
Screen:
name: 'screen_two'
Button:
text: root.statusmsg
font_size: base_font_size
disabled: True if root.statusmsg == 'Busy launching Armageddon' else False # prevent multiple activation
on_press:
root.deliver_payload()
''')
class MainWidget(FloatLayout):
statusmsg = StringProperty()
def __init__(self, **kwargs):
super(MainWidget, self).__init__(**kwargs)
def deliver_payload(self, dt=0):
if not dt: # called via on_press
self.statusmsg = 'Busy launching Armageddon'
# launch Armageddon here
Clock.schedule_once(self.deliver_payload, 2)
else: # scheduled via Clock
self.manager.current = 'screen_one'
class MyApp(App):
def build(self):
mw=MainWidget()
return mw
if __name__ == '__main__':
MyApp().run()
However, manager.current is a Kivy StringProperty and I should be able to assign a new value to it with the set() method and perhaps schedule this with Clock e.g. Clock.schedule_once(lambda dt: self.manager.property('current').set(??, 'screen_one'), 2).
I wasn't able to find documentation for Kivy StringProperty set() method. It seems the method takes two args and the first argument needs to be of type kivy._event.EventDispatcher - according to traceback info that I get when I try some random guesses. Can anyone point to some documentation, or examples of use for the set() method?
EDIT: I realise I did not make it clear what I want to do ultimately - I am asking if it is possible to schedule the Kivy property set() method using Kivy Clock. For example, I am able to toggle a Kivy BooleanProperty like this:
if self.property('myboolean').get(self):
self.property('myboolean').set(self, False)
else:
self.property('myboolean').set(self, True)
But I was not able to schedule the method using Clock. The following line generated no errors but did not have any effect either:
Clock.schedule_once(lambda dt: self.property('myboolean').set(self, False),0)
In the case of Kivy StringProperty set() method, I was not even able to figure out what the 1st argument needed to be, so did not get as far as trying to schedule it with Clock.
FURTHER EDIT:
Although screen manager 'current' is a StringProperty according to documentation, it appears to behave somewhat differently. With a StringProperty I am able to do the following:
self.property('statusmsg').set(self, 'Armageddon now')
However, attempting something like this with manager.current does not succeed:
self.manager.property('current').set(self.manager, 'aux_screen')
The error message is:
self.manager.property('current').set(self.manager, 'screen_one')
TypeError: Argument 'obj' has incorrect type (expected kivy._event.EventDispatcher, got kivy.weakproxy.WeakProxy)
Confusing.

Answer 1

I stumbled across this by chance Kivy: Changing screens in screen manager with an on_press event (thank you, Tshirtman) and I now have one answer. The following change gives me what I want - the ability to schedule screen change directly (i.e. without an intermediate method to call):
def deliver_payload(self):
self.statusmsg = 'Busy launching Armageddon'
Clock.schedule_once(lambda dt: self.manager.setter('current')(self.manager,'screen_one'), 2)
So it appears that for assigning a new value to screen manager's 'current' property, the correct method to use is the 'setter' method (not the 'set' method that I was attempting to use).

Answer 2

You can set a new value for a StringProperty by simply doing a self.manager.current = 'some string', as you do in your code.