尝试更改屏幕时出现 Kivy 错误

Question

我不想使用.kv 语言。因此，当我按下按钮时尝试运行功能时会出现我的问题。
我发现这些问题有同样的问题，所以我从他们那里采用了 on_press 方法的代码：
kivy python passing parameters to fuction with button click
Python, Kivy, “AssertionError: None is not callable” Error on function call by button

错误

File "kivy\_event.pyx", line 703, in kivy._event.EventDispatcher.dispatch
   File "kivy\_event.pyx", line 1214, in kivy._event.EventObservers.dispatch
   File "kivy\_event.pyx", line 1138, in kivy._event.EventObservers._dispatch
   File "C:\Users\schup\PycharmProjects\Workspace\kivy_app_go\Surface.py", line 28, in <lambda>
     btnHvH = Button(text="Human vs Human", size_hint=(0.35, 0.15), on_release=lambda *args: self.HelperMethodsInst.switch_screen(goal_screen="go_screen", Screenmanager=WindowManager.get_ScreenManager, *args))
 TypeError: switch_screen() got multiple values for argument 'Screenmanager'

Surface.py：

from kivy.app import App
from kivy.lang import Builder
from kivy.uix.screenmanager import ScreenManager, Screen
from kivy_app_go.Control import HelperMethods
from kivy.properties import ObjectProperty
from kivy.graphics import Rectangle, Color, Line
from kivy.uix.label import Label
from kivy.uix.floatlayout import FloatLayout
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.button import Button
from kivy.core.window import Window
from kivy.uix.screenmanager import FadeTransition

from functools import partial


class MenuScreen(Screen):
    def __init__(self, **kwargs):
        super(Screen, self).__init__(**kwargs)
        self.ScreenSize = Window.size
        self.HelperMethodsInst = HelperMethods()

        lytmain = FloatLayout(size=self.ScreenSize)
        lytbutton = BoxLayout(pos_hint={"y": 0.1, "x": 0.15}, size_hint=(2, 0.6), orientation='vertical', size=self.ScreenSize)

        lblHeadline = Label(text="Choose your Go Mode", font_size=40, pos_hint={"y": 0.8, "x": 0.325},
                            size_hint=(0.35, 0.15))
        btnHvH = Button(text="Human vs Human", size_hint=(0.35, 0.15), on_release=lambda *args: self.HelperMethodsInst.switch_screen(goal_screen="go_screen", Screenmanager=WindowManager.get_ScreenManager, *args))
        btnHvB = Button(text="Human vs Bot", size_hint=(0.35, 0.15), on_release=lambda *args: self.HelperMethodsInst.switch_screen(goal_screen="go_screen", Screenmanager=WindowManager.get_ScreenManager, *args))
        btnBvB = Button(text="Bot vs Bot", size_hint=(0.35, 0.15), on_release=lambda *args: self.HelperMethodsInst.switch_screen(goal_screen="go_screen", Screenmanager=WindowManager.get_ScreenManager, *args))

        self.add_widget(lytmain)
        lytmain.add_widget(lblHeadline)
        lytmain.add_widget(lytbutton)
        lytbutton.add_widget(btnHvH)
        lytbutton.add_widget(btnHvB)
        lytbutton.add_widget(btnBvB)



class GoScreen(Screen):
    def __init__(self, **kwargs):
        super(GoScreen, self).__init__(**kwargs)
        self.ScreenSize = Window.size

        lytmain = FloatLayout(size=self.ScreenSize)

        btnBack = Button(text="Back", size_hint=(0.25, 0.1))

        self.add_widget(lytmain)
        lytmain.add_widget(btnBack)


class WindowManager(ScreenManager):
    def __init__(self):
        self.sm = ScreenManager(transition=FadeTransition(duration=0.15))
        self.sm.add_widget(MenuScreen(name="menu_screen"))
        self.sm.add_widget(GoScreen(name="go_screen"))

    @property
    def get_ScreenManager(self):
        return self.sm

class Surface(App):
    def __init__(self):
        super().__init__()
        self.WindowManagerInst = WindowManager()

    def build(self):
        return self.WindowManagerInst.sm

    @staticmethod
    def create_Surface():
        return Surface().run()


def run():
    SurfaceInst = Surface()
    HelperMethodsInst = HelperMethods()

Control.py：

from kivy.uix.screenmanager import ScreenManager, Screen


class HelperMethods:
    def switch_screen(self, Screenmanager, goal_screen):
        screenmanager = goal_screen

ma​​in.py:

from kivy_app_go.Surface import Surface

if __name__ == "__main__":
    Surface.create_Surface()

我是 kivy 的新手。
我希望有人可以帮助^^

Answer 1

你得到了

参数“屏幕管理器”的多个值

错误，因为您的 lambda 正在构造一个带有关键字参数的函数，后跟 *args。由于位置参数必须在关键字参数之前，您的*args 被视为Screenmanager= 关键字的一部分。因此，该关键字将传递给您的 switch_screen 方法

Screenmanager = WindowManager.get_ScreenManager, *args

如果您需要将 Button 实例（*args 是什么）传递给您的 switch_screen 方法，那么您需要修改该方法以接受它（并调整 lambda）。

您只需从lambda 的末尾删除*args 即可避免该错误。

但是，同一行代码中还有另一个问题。您正在使用WindowManager.get_ScreenManager，但WindowManager 是一个类，而不是一个实例，并且在类文件中get_ScreenManager 是一个属性。所以您需要WindowManager 实例，您可以从App 的WindowManagerInst 属性中获取该实例。因此，该行现在变为：（以及获取正在运行的 App 的调用）：

app = App.get_running_app()
btnHvH = Button(text="Human vs Human", size_hint=(0.35, 0.15), on_release=lambda *args: self.HelperMethodsInst.switch_screen(goal_screen="go_screen", Screenmanager=app.WindowManagerInst.get_ScreenManager))