ScreenManager 中的随机屏幕 python kivy

Question

I have in my app some images, each image belongs to a screen and when I press a button I try to get another screen but a random one. I think I am pretty close to do what I want to do but for 2 days I am stuck at this stage.. when i run my code in the console i have this error " AttributeError: 'ScreenManager' object has no attribute 'random_screen' "

And I really don't know where to put that attribute... please heeeelppp: :((

from kivy.app import App
from kivy.uix.screenmanager import ScreenManager, Screen
from random import choice


class MyScreens(Screen):
    screens = ["Q1", "Q2", "Q3"]  # ........

    def __init__(self, **kwargs):
        super().__init__(**kwargs)
        self.random_screen()

    def random_screen(self, *_):
        self.source = choice(self.screens)


class Q1(Screen):
    pass


class Q2(Screen):
    pass


class Q3(Screen):
    pass


class TestApp(App):

    def build(self):

        sm = ScreenManager()
        sm.add_widget(Q1(name='Q1'))
        sm.add_widget(Q2(name='Q2'))
        sm.add_widget(Q2(name='Q3'))

        return sm


if __name__ == '__main__':
    TestApp().run()

<Q1>:
    Image:
        source: 'Q1.png'

        FloatLayout:
            size: root.width, root.height/2

            Button:
                size_hint: 0.3, 0.25
                pos_hint: {"x":0.09, "top":1.16}
                background_color: 1, 1, 1, 0.2
                on_release: app.root.random_screen()

<Q2>:
    Image:
        source: 'Q2.png'

        FloatLayout:
            size: root.width, root.height/2

            Button:
                size_hint: 0.3, 0.25
                pos_hint: {"x":0.09, "top":1.16}
                background_color: 1, 1, 1, 0.2
                on_press: app.root.random_screen()

<Q3>:
    Image:
        source: 'Q3.png'

        FloatLayout:
            size: root.width, root.height/2

            Button:
                size_hint: 0.3, 0.25
                pos_hint: {"x":0.09, "top":1.16}
                background_color: 1, 1, 1, 0.2
                on_press: app.root.random_screen()

Answer 1

You got a lot of bugs in there...

1. Myscreen class isn't connected to your other classes or kv file at all, so that function will not be found at all.

2. Your 3rd add.widget call adds the 'Q2' screen instead of Q3

3. Screen does not have a self.source parameter. You need to use the screenmanager to change screens. root.manager.current = 'Q#' would be the correct way.

This worked for me...

from kivy.app import App
from kivy.uix.screenmanager import ScreenManager, Screen
import random


class Q1(Screen):
    def random_screen(self):
        screens = ['Q1', 'Q2', 'Q3']
        return random.choice(screens)



class Q2(Screen):
    def random_screen(self):
        screens = ['Q1', 'Q2', 'Q3']
        return random.choice(screens)


class Q3(Screen):
    def random_screen(self):
        screens = ['Q1', 'Q2', 'Q3']
        return random.choice(screens)


class TestApp(App):

    def build(self):

        sm = ScreenManager()
        sm.add_widget(Q1(name='Q1'))
        sm.add_widget(Q2(name='Q2'))
        sm.add_widget(Q3(name='Q3'))

        return sm


if __name__ == '__main__':
    TestApp().run()

KV file

<Q1>:
    Image:
        source: 'Q1.png'

        FloatLayout:
            size: root.width, root.height/2

            Button:
                size_hint: 0.3, 0.25
                pos_hint: {"x":0.09, "top":1.16}
                background_color: 1, 1, 1, 0.2
                on_release: root.manager.current = root.random_screen()
<Q2>:
    Image:
        source: 'Q2.png'

        FloatLayout:
            size: root.width, root.height/2

            Button:
                size_hint: 0.3, 0.25
                pos_hint: {"x":0.09, "top":1.16}
                background_color: 1, 1, 1, 0.2
                on_release: root.manager.current = root.random_screen()
<Q3>:
    Image:
        source: 'Q3.png'

        FloatLayout:
            size: root.width, root.height/2

            Button:
                size_hint: 0.3, 0.25
                pos_hint: {"x":0.09, "top":1.16}
                background_color: 1, 1, 1, 0.2
                on_release: root.manager.current = root.random_screen()

Answer 2

You could also put the method in the app class and in the kv file call it by using

app.random_screen()

Just means you don't have to repeat the same method in each screen class.

from kivy.app import App
from kivy.uix.screenmanager import ScreenManager, Screen
import random


class Q1(Screen):
    Pass

class Q2(Screen):
    Pass

class Q3(Screen):
    Pass


class TestApp(App):

    def random_screen(self):
        screens = ['Q1', 'Q2', 'Q3']
        return random.choice(screens)

    def build(self):

        sm = ScreenManager()
        sm.add_widget(Q1(name='Q1'))
        sm.add_widget(Q2(name='Q2'))
        sm.add_widget(Q3(name='Q3'))

        return sm


if __name__ == '__main__':
    TestApp().run()

kV:

<Q1>:
    Image:
        source: 'Q1.png'

        FloatLayout:
            size: root.width, root.height/2

            Button:
                size_hint: 0.3, 0.25
                pos_hint: {"x":0.09, "top":1.16}
                background_color: 1, 1, 1, 0.2
                on_release: root.manager.current = app.random_screen()

<Q2>:
    Image:
        source: 'Q2.png'

        FloatLayout:
            size: root.width, root.height/2

            Button:
                size_hint: 0.3, 0.25
                pos_hint: {"x":0.09, "top":1.16}
                background_color: 1, 1, 1, 0.2
                on_release: root.manager.current = app.random_screen()

<Q3>:
    Image:
        source: 'Q3.png'

        FloatLayout:
            size: root.width, root.height/2

            Button:
                size_hint: 0.3, 0.25
                pos_hint: {"x":0.09, "top":1.16}
                background_color: 1, 1, 1, 0.2
                on_release: root.manager.current = app.random_screen()

Another thing to consider, and I am not sure how this would work as I haven't used images like the way you are doing, but you could have the button change the image rather then change the screen... In the app class you could have a string property that is changed in the same way the button changes your screen. In the kv file, have the image source reference this string property, app.Pic for example below...

from kivy.app import App
from kivy.uix.properties import StringProperty 
from kivy.uix.screenmanager import ScreenManager, Screen
import random


class Q1(Screen):
    Pass


class TestApp(App):
    Pic = StringProperty('Q1.png')

    def random_pic(self):
        Pics = ['Q1.png', 'Q2.png', 'Q3.png']
        self.Pic = random.choice(Pics)

    def build(self):

        sm = ScreenManager()
        sm.add_widget(Q1(name='Q1'))
        

        return sm


if __name__ == '__main__':
    TestApp().run()

kV:

<Q1>:
    Image:
        source: app.Pic

        FloatLayout:
            size: root.width, root.height/2

            Button:
                size_hint: 0.3, 0.25
                pos_hint: {"x":0.09, "top":1.16}
                background_color: 1, 1, 1, 0.2
                on_release: app.random_pic()

Answer 3

I know this isnt another answer to your original question but as per the above comment here is a really paired back quiz app, to give you an idea of how you can change the question and the answers and use the same buttons and screen...

I put everything into the app class, it makes it easier to access from the kv file. I tried to add in a few comments to try and expalin the code

from kivy.app import App
from kivy.properties import StringProperty, BooleanProperty,ObjectProperty, NumericProperty
from kivy.uix.screenmanager import ScreenManager, Screen


TestBank = {1 : {"Current Question": "Press 3", "Correct Answer": "3", "Chosen Answer": "", "Multiple Chocies": ["1","2","3","4"]},
2 : {"Current Question": "Press 4", "Correct Answer": "4", "Chosen Answer": "", "Multiple Chocies": ["1","2","3","4"]},
3 : {"Current Question": "Press 1", "Correct Answer": "1", "Chosen Answer": "", "Multiple Chocies": ["1","2","3","4"]},
4 : {"Current Question": "Press 2", "Correct Answer": "2", "Chosen Answer": "", "Multiple Chocies": ["1","2","3","4"]}}

def CreateTest(A_Test = TestBank):
    #do something to randomise your test, maybe select a certain number of questions or merge several test banks etc...
    return A_Test


class MenuScreen(Screen):
    pass

class ResultScreen(Screen):
    pass

class TestScreen(Screen):
    pass

class QuizApp(App):


    TestCurrentQuestion = StringProperty()
    'This is updated when next question is selcted'

    ChosenAnswerText = StringProperty()
    'Every time an answer is selected this property is updated with the selected answer, then the label is automatically updated'
    
    CurrentQuestion = NumericProperty(1)
    'The Next and Previous buttons change this property up or down'
    
    TotalQuestions = 4


    AnswerButtonA = StringProperty()
    AnswerButtonB = StringProperty()
    AnswerButtonC = StringProperty()
    AnswerButtonD = StringProperty()
    'These are the four answer buttons, the Next and Previous buttons update these properties with the answer options, the button texts are then autmatically updated'


    Score = NumericProperty()



    def StartTest(self):
        self.Test = CreateTest()                    #The test is created
        self.UpdateQuestionAndAnswerButtons()       #This method updates the text properties that updates all the buttons

    def NextQuestion(self):
        self.CurrentQuestion +=1                    #changes the current question property +1
        self.UpdateQuestionAndAnswerButtons()       #This method updates the text properties that updates all the buttons
                      
    def PreviousQuestion(self):
        self.CurrentQuestion -=1                    #changes the current question property -1      
        self.UpdateQuestionAndAnswerButtons()       #This method updates the text properties that updates all the buttons

    def UpdateChosenAnswer(self, button):
        self.Test[self.CurrentQuestion]["Chosen Answer"] = button.text              #so that a score can be calculated, the chosen answer is stored in the dictionary TestBank
        self.ChosenAnswerText = self.Test[self.CurrentQuestion]["Chosen Answer"]    #ChosenAnswerProperty is updated, this then updates the label so the chosen answer appears on screen

    def UpdateQuestionAndAnswerButtons(self):
        self.TestCurrentQuestion = self.Test[self.CurrentQuestion]["Current Question"]          
        #TestCurrentQuestion is the property, it is updated to ["Current Question"] for the Test Dic
        
        self.AnswerButtonA, self.AnswerButtonB, self.AnswerButtonC, self.AnswerButtonD = self.Test[self.CurrentQuestion]["Multiple Chocies"]        
        #["Multiple Chocies"] is a list containing 4 items, so the four properties are updated in one line
        
        self.ChosenAnswerText = self.Test[self.CurrentQuestion]["Chosen Answer"]                
        #The chosen answer is updated, this is needed here incase the previous button is selcted, the previous selected answer will be updated to avoid confusion for the user


    def CalculateScore(self):
        score = 0
        for Question in self.Test.keys():
            if self.Test[Question]["Chosen Answer"]== self.Test[Question]["Correct Answer"]:
                score+=1
        self.Score =  score
        

    def build(self):
        sm = ScreenManager()
        sm.add_widget(MenuScreen(name='menu'))
        sm.add_widget(ResultScreen(name='result'))
        sm.add_widget(TestScreen(name='test'))


        return sm
    
QuizApp().run()

And the KV file

<ResultScreen>
    BoxLayout:
        orientation: "vertical"
        padding: "20px"
        spacing: "20px"

        BoxLayout:
            Label:
                text: f"Your Score was {app.Score} out of {app.TotalQuestions}\n                   {round(app.Score/app.TotalQuestions*100)}%"
            Label:
                text: "PASS" if app.Score/app.TotalQuestions*100 >= 70 else "FAIL" #pass mark is 70%
    
        Button:
            text: "Good Bye"
            on_press: app.get_running_app().stop()
   

<MenuScreen>
    BoxLayout:
        orientation: "vertical"
        padding: "20px"
        spacing: "20px"
        
        Label:
            text:"Wecome to the  Test App"

        Button:
            text: "New Test"
            on_press: app.StartTest(); root.manager.current = "test"


<TestScreen>
    BoxLayout:
        orientation: "vertical"

        BoxLayout:
            padding: "20px"
            orientation: "vertical"

            Label:
                text: app.TestCurrentQuestion
                halign: "center"
            Label:
                text: app.ChosenAnswerText

        GridLayout:
            padding: "20px"
            spacing: "20px"
            cols: 2
            rows: 2
            
            Button:
                text: app.AnswerButtonA
                on_press: app.UpdateChosenAnswer(self)

            Button:
                text: app.AnswerButtonB
                on_press: app.UpdateChosenAnswer(self)

            Button:
                text: app.AnswerButtonC
                on_press: app.UpdateChosenAnswer(self)

            Button:
                text: app.AnswerButtonD
                on_press: app.UpdateChosenAnswer(self)
                  
        BoxLayout:

            size_hint: (1,None)
            orientation: "horizontal"
            padding: "20px"
            spacing: "20px"

            Button:
                text: "Previous"
                size_hint: (0.3,1)
                on_press: app.PreviousQuestion()
                disabled: True if app.CurrentQuestion == 1 else False

            Button:
                text: "Submit"
                size_hint: (0.4,1)
                on_press: app.CalculateScore(); root.manager.current = "result"

            Button:
                text: "Next"
                on_press: app.NextQuestion(); 
                size_hint: (0.3,1)
                disabled: True if app.CurrentQuestion  == app.TotalQuestions else False