Kivy No Screen with name - python-3.x

Question

In my main.py:
class WelcomeScreen(Screen):
pass
class SignupScreen(Screen):
username = ObjectProperty(None)
def submit(self):
db.add_user(self.username.text)
self.reset()
self.root.current = "login"
def login(self):
self.reset()
self.current = "signup"
def reset(self):
self.username.text = ""
class LoginScreen(Screen):
pass
class WindowManager(ScreenManager):
def __init__(self, *args, **kwargs):
super().__init__(*args, **kwargs)
Clock.schedule_once(self.screen_switch_signup, 2)
def screen_switch_signup(self, time):
self.current = 'signup'
db = DataBase()
class mainApp(App):
kv_directory = 'kv'
def build(self):
return WindowManager()
if __name__ == '__main__':
mainApp().run()
Then,my main.kv:
#:import SlideTransition kivy.uix.screenmanager.SlideTransition
WindowManager:
name: "screen_manager"
transition: SlideTransition()
WelcomeScreen:
name: "welcome"
#: include kv/signupScreen.kv
manager: 'screen_manager'
SignupScreen:
name: "signup"
#: include kv/signupScreen.kv
manager: 'screen_manager'
LoginScreen:
name: "login"
#: include kv/loginScreen.kv
manager: 'screen_manager'
Finally, I have 3 kv files:
My signupScreen.kv
<SignupScreen>:
username: username
TextInput:
id: username
hint_text: "Username"
Button:
text: "SIGN UP"
on_release:
app.root.transition.direction = "right"
root.submit()
my loginScreen.kv
<LoginScreen>:
BoxLayout:
orientation: 'vertical'
Label:
id: email
text: "Your email"
Button
id: go_back_screen_1
text: 'Go back'
on_release:
app.root.current = 'signup'
root.manager.transition.direction = 'right'
And finally the welcomeScreen.kv
<WelcomeScreen>:
Label:
text: "Welcome"
When I launch, I get the error:
File "kivy_clock.pyx", line 218, in kivy._clock.ClockEvent.tick
File "\Git\main.py",
line 89, in screen_switch_signup
self.current = 'signup'
kivy.uix.screenmanager.ScreenManagerException: No Screen with name
"signup".
I'm pretty new to Kivy, so I don't understand what's happening here.
The architecture is like that:
* myApp
* main.py
* kv
* main.kv
* loginScreen.kv
* signupScreen.kv
* welcomeScreen.kv
Any one knows please?

Answer 1

I have found several moments that can raise the error:
Here kv_directory = 'kv' you tell where all of your kv files are located. It means there should be a directory kv in your project directory. Make sure you have this directory and all kv files in it.
You should use <WindowManager>: instead of WindowManager: in your main.kv because you want to define (discribe) WindowManager class but not to add it to your app.
These hints should fix your app
Edit: I didn't catch sight of you've added the architecture of your project. Then just do the second point