CODEWITHSUNDEEP
pythonkivykivy-language
Sam Bennett
Sam Bennett

Reputation: 51

Kivy: How to run the same function across several screens

I am trying to make a timer that counts down to zero from a random starting number repeatedly until a predetermined time limit is reached. I have managed to do this on one screen, but I am having trouble adapting it to several screens.

Currently, if I run the functions in the PleaseWork(boxLayout) class it does exactly as it should. However, I would like to add in some screens so that the home screen has a button that says "Go!" and on release of the button the timer is started. I would like to be able to cycle from the second to third screen with the value on the timer being exactly the same, but I am unsure of how to do this.

Py File:

from kivy.app import App
from kivy.lang import Builder
from kivy.uix.screenmanager import ScreenManager, Screen
from kivy.animation import Animation
from kivy.properties import NumericProperty
from random import randint


class MainWindow(Screen):
    pass

class SecondWindow(Screen):
    pass

class ThirdWindow(Screen):
    pass

class WindowManager(ScreenManager):
    pass

class PleaseWork(App):
    a = NumericProperty(0)
    b = NumericProperty(0)
    run_t= 15
    min = 3
    max = 7

    def start(self):
        self.a = randint(self.min, self.max)
        self.anim = Animation(a=0, duration=self.a)
        if self.run_t - self.b <= self.max:
            self.a = self.run_t - self.b
            print("a=",self.a,"b=",self.b)
            self.anim = Animation(a=0, duration = self.a)
        else:
            print(self.run_t - self.b)
            self.anim.bind(on_complete = self.start)
        print('starting anim number:', self.lap_counter)
        self.anim.start(self)

    def count_up(self):
        self.anim = Animation(b = self.run_t, duration = self.run_t)
        self.anim.bind(on_complete = self.finish_callback)
        self.anim.start(self)

    def finish_callback(self, animation, param):
        print('in finish_callback')
        end_1 = self.ids['count_down']
        end_1.text = 'Finished'
        Animation.cancel_all(self)


kv = Builder.load_file("integrate.kv")

class PageScrollerApp(App): 
    def build(self): 
        return kv

if __name__ == "__main__":
    PageScrollerApp().run()

kv file:

WindowManager:
    MainWindow:
    SecondWindow:
    ThirdWindow:


<MainWindow>:
    name: "home"

    FloatLayout:
        Button:
            pos_hint: {"x":0.4, "y":0.05}
            text: "Go!"
            on_release:
                app.root.current = 'low'


<SecondWindow>:
    name: 'low'

    FloatLayout:
        Label:
            id: count_down1
            text: str(round(root.a, 1))
            pos_hint: {"x": 0.4, "y": 0.55}
        Button:
            background_color: 0.5,0.1,1,1
            text: 'next'
            pos_hint: {"x":0.4, "y":0.05}
            on_release:
                app.root.current = "medium"

<ThirdWindow>:
    name: "medium"

    FloatLayout:
        Label:
            id: count_down2
            text: str(round(root.a, 1))
            pos_hint: {"x": 0.4, "y": 0.55}
        Button:
            background_color: 0.5,0.1,1,1
            text: 'Cancel'
            pos_hint: {"x":0.4, "y":0.05}
            on_release:
                app.root.current = "home"

<Button>
    font_size: 20
    color:1,0.2,0.5,1
    size_hint: 0.2, 0.1
    background_color: 0.5,0.8,0.2,1

<Label>
    font_size: 20
    color:1,0.2,0.5,1
    size_hint: 0.2, 0.1
    background_color: 0.5,0.2,0.9,1

Currently if I try to run the program it comes up with the following error message:

AttributeError: 'SecondWindow' object has no attribute 'a'

But I also realise I am not actually calling the functions inside the PleaseWork(App) class at any point. I just have been unable to work out how. Sorry if the answer is obvious, but I am new to using kivy!

Upvotes: 0

Views: 259

Answers (1)

ikolim
ikolim

Reputation: 16031

Problem - AttributeError 'a'

AttributeError: 'SecondWindow' object has no attribute 'a'

Root Cause

The class attribute, a is only defined in the class PleaseWork() and this class is not the root. The root is class WindowManager().

Other Problems

  • Two app classes defined
  • Missing attribute, self.lap_counter
  • Missing kv id: count_down in self.ids['count_down']

Solution

The following enhancements are needed in the py and kv files.

py file

  • Remove pass from class WindowManager(), and class header, class PleaseWork(App)
  • Implement a method reset() to reset a and b to zero
  • Add *args as arguments in method start()

Snippets - py file

class WindowManager(ScreenManager):
    a = NumericProperty(0)
    b = NumericProperty(0)
    run_t = 15
    min = 3
    max = 7

    def reset(self):
        self.a = 0
        self.b = 0

    def start(self, *args):
        self.a = randint(self.min, self.max)
        self.anim = Animation(a=0, duration=self.a)
        if self.run_t - self.b <= self.max:
            self.a = self.run_t - self.b
            print("a=", self.a, "b=", self.b)
            self.anim = Animation(a=0, duration=self.a)
        else:
            print(self.run_t - self.b)
            self.anim.bind(on_complete=self.start)
        # print('starting anim number:', self.lap_counter)
        self.anim.start(self)

    def count_up(self):
        self.anim = Animation(b=self.run_t, duration=self.run_t)
        self.anim.bind(on_complete=self.finish_callback)
        self.anim.start(self)

    def finish_callback(self, animation, param):
        print('in finish_callback')
        end_1 = self.ids['count_down']
        end_1.text = 'Finished'
        Animation.cancel_all(self)


class PageScrollerApp(App):
    def build(self):
        return Builder.load_file("integrate.kv")

kv file

  • Invoke methods reset() and start() in on_release event of "Go" button
  • Replace all occurrences of root.a with root.manager.a

Snippets - kv file

<MainWindow>:
    name: "home"

    FloatLayout:
        Button:
            pos_hint: {"x":0.4, "y":0.05}
            text: "Go!"
            on_release:
                root.manager.reset()
                root.manager.start()
                root.manager.current = 'low'

<SecondWindow>:
    name: 'low'

    FloatLayout:
        Label:
            id: count_down1
            text: str(round(root.manager.timer.a, 1))
            pos_hint: {"x": 0.4, "y": 0.55}
        Button:
            background_color: 0.5,0.1,1,1
            text: 'next'
            pos_hint: {"x":0.4, "y":0.05}
            on_release:
                root.manager.current = "medium"

<ThirdWindow>:
    name: "medium"

    FloatLayout:
        Label:
            id: count_down2
            text: str(round(root.manager.timer.a, 1))
            pos_hint: {"x": 0.4, "y": 0.55}
        Button:
            background_color: 0.5,0.1,1,1
            text: 'Cancel'
            pos_hint: {"x":0.4, "y":0.05}
            on_release:
                root.manager.current = "home"

Output

SecondWindow ThirdWindow

Upvotes: 2

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