Kivy ScreenManager不切换屏幕

Question

i am a newbie to both python and kivy. I have been trying to develop a simple Pong game with Python. Everything was going well until i tried to put together a Menu. I used ScreenManager to try to navigate through the two screens. But when i press the button, nothing happens. Every answer or idea is well appreciated!

Here is my .py code:

from kivy.app import App
from kivy.uix.widget import Widget
from kivy.properties import NumericProperty, 
ReferenceListProperty,ObjectProperty
from kivy.vector import Vector
from kivy.clock import Clock
import pygame 
from kivy.uix.button import Button
from kivy.uix.screenmanager import ScreenManager, Screen
from kivy.uix.gridlayout import GridLayout
from kivy.lang import Builder


class Menu(GridLayout,Screen):

def __init__(self, **kwargs):
    super(Menu, self).__init__(**kwargs)
pass

class PongSpadi(Widget):
stig = NumericProperty(0)

def skoppa_bolti(self, bolti):
    if self.collide_widget(bolti):
        vx, vy = bolti.velocity
        offset = (bolti.center_y - self.center_y) / (self.height / 2)
        skoppadur = Vector(-1 * vx, vy)
        vel = skoppadur
        bolti.velocity = vel.x, vel.y + offset

class PongBolti(Widget):
velocity_x = NumericProperty(0)
velocity_y = NumericProperty(100)
velocity = ReferenceListProperty(velocity_x, velocity_y)


def move(self):
    self.pos = Vector(*self.velocity) + self.pos 


class PongGame(Screen, Widget):
bolti = ObjectProperty(None)
spilari1 = ObjectProperty(None)
spilari2 = ObjectProperty(None)
h1 = NumericProperty(310)
h2 = NumericProperty(310)


def serve_bolti(self, vel=(12, 6)):

    self.bolti.center = self.center #Staðsetur boltann í miðjuna
    self.bolti.velocity = vel

def update(self, dt): 
    self.bolti.move()

    self.spilari1.skoppa_bolti(self.bolti) #skoppar bolta af spöðum
    self.spilari2.skoppa_bolti(self.bolti)

    if (self.bolti.y < 0) or (self.bolti.top > self.height):
            self.bolti.velocity_y *= -1 #Lætur boltan skoppa ef hann snertir vegginn uppi/niðri


    if self.bolti.x <self.x: 
        self.spilari2.stig += 1 #skráir stig ef bolti fer í hliðarnar
        self.serve_bolti(vel= (12,6)) #byrjar nýtt uppkast    
    if self.bolti.x > self.width:
        self.spilari1.stig += 1
        self.serve_bolti(vel = (-12,6))

    keys = pygame.key.get_pressed()  #Takka stjórnun fyrir leikmann 1
    if self.h1 < 567: #Bannar spaða 1 að fara of hátt
        if self.h1 > 25: #Bannar spaða 1 að fara of látt
            if keys[pygame.K_z]: #býr til takka fyrir spaða 1
                self.h1 -= 10
            elif keys[pygame.K_a]:
                self.h1 += 10
        if self.h1 >= 567: #ýtir honum til baka ef farið er of hátt
            self.h1 -= 10
        if self.h1 <= 25: #ýtir honum til baka ef farið er of látt
            self.h1 += 10

    keys = pygame.key.get_pressed() #takka stjórnun fyrir leikmann 2
    if self.h2 < 567:   
        if self.h2 > 25:
            if keys[pygame.K_m]:
                self.h2 -= 10
            elif keys[pygame.K_k]:
                self.h2 += 10
        if self.h2 >= 567: #ýtir honum til baka ef farið er of hátt
            self.h2 -= 10
        if self.h2 <= 25: #ýtir honum til baka ef farið er of látt
            self.h2 += 10
    pass

sm = ScreenManager()
sm.add_widget(Menu(name='menu'))
sm.add_widget(PongGame(name='ponggame'))       

class PongApp(App): #ræsir forritið
title = "Menu"
def build(self):    #kallar á eiginleika leiksins
    sm = Menu()
    return sm

    sm = PongGame()
    sm.serve_bolti()   #kallar á uppkast boltans
    Clock.schedule_interval(sm.update, 1.0 / 60) #Lætur leikinn uppfærast 60 sinnum á sekúndu.
    return sm



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

And here is my .kv code:

#: kivy 1.9.1

ScreenManager:
    Menu:
    PongGame:

<Menu>
    name: 'menu'

Button:
    on_press: app.root.current = 'ponggame'
    on_press: print("virkar")
    text: "Manneskja á móti manneskju"
    font_size: 20
    center_x: root.width / 2
    top: root.top / 1.5
    size: 275, 50

Label: #nafn á leik
    font_size: 100
    center_x: root.width / 2
    top: root.top - 50
    text: 'Pong og Gervigreind'

Label:
    font_size: 20
    center_x: root.width / 2
    top: root.top -120
    text: 'Lokaverkefni eftir Hróbjart Höskuldsson vor 2018'





<PongBolti>:
size: 20, 20
canvas: 
    Rectangle:
        pos: self.pos
        size: self.size

<PongSpadi>:
size: 23, 100
canvas:
    Rectangle:
        pos:self.pos
        size:self.size      



<PongGame>:  
name: 'ponggame'

bolti: pong_bolti
spilari1: spilari_vinstri
spilari2: spilari_haegri

canvas:
    Rectangle:
        pos: self.center_x - 5, 0
        size: 3, self.height

Label:  # staða leikmanns 1
    font_size: 70  
    center_x: root.width / 4
    top: root.top - 50
    text: str(root.spilari1.stig)

Label:  # staða leikmanns 2
    font_size: 70  
    center_x: root.width * 3 / 4
    top: root.top - 50
    text: str(root.spilari2.stig)

PongBolti:
    id: pong_bolti
    center: self.parent.center

PongSpadi:
    id: spilari_vinstri
    x: root.x + 30
    center_y: root.h1

PongSpadi:
    id: spilari_haegri
    x: root.width-self.width - 30
    center_y: root.h2

Button:
    on_release: app.root.current = 'menu'
    on_press: print("virkar")
    text: "Manneskja á móti manneskju"
    font_size: 20
    center_x: root.width / 2
    top: root.top / 1.5
    size: 275, 50    

Answer 1

This is not a complete answer, but some ideas to get you moving:

1. Your build() method should return a ScreenManager . I think it should look something like this:

    def build(self): #kallar á eiginleika leiksins sm = ScreenManager() sm.add_widget(Menu()) sm.add_widget(PongGame()) return sm 

2. Your PongGame does not need to extend Widget ( Screen is a Widget)

3. Your Menu class does not need to extend both Screen and GridLayout . Just use a GridLayout in your Menu like this:

    <Menu> name: 'menu' GridLayout: rows: 3 Button: on_press: app.root.current = 'ponggame' on_press: print("virkar") text: "Manneskja á móti manneskju" font_size: 20 center_x: root.width / 2 top: root.top / 1.5 size: 275, 50 Label: #nafn á leik font_size: 100 center_x: root.width / 2 top: root.top - 50 text: 'Pong og Gervigreind' Label: font_size: 20 center_x: root.width / 2 top: root.top -120 text: 'Lokaverkefni eftir Hróbjart Höskuldsson vor 2018' 

4. You have code in your build() method that looks like it might be starting the game. I think that might be better in the on_enter() method of PongGame .