如何使用 python 和 kivy 获取函数外的值

Posted 2023-04-14

【中文标题】如何使用 python 和 kivy 获取函数外的值

【英文标题】：How to get value outside function using python and kivy

【发布时间】：2020-09-28 00:10:17

【问题描述】：

这是一个简单的 python kivy 应用程序，只有文本标签和滑块。此代码运行良好。

from kivy.uix.screenmanager import ScreenManager, Screen
from kivy.uix.floatlayout import FloatLayout
from kivymd.app import MDApp
from kivymd.theming import ThemeManager
from kivymd.uix.slider import Slider
from kivy.properties  import NumericProperty
from kivymd.uix.label import MDLabel

class Screen1(Screen):
    def __init__(self, **kwargs):
        super(Screen1, self).__init__(**kwargs)
        layout = FloatLayout()

        self.hours_value = MDLabel(text = "0", halign = "center", pos_hint = 'center_x':.5, 'center_y':.80, theme_text_color = 'Error')
        self.hours_slider = Slider(min = 0, max = 24, pos_hint = 'center_x':.5, size_hint_x = .7)
        self.hours_slider.bind(value = self.on_value_hours)

        layout.add_widget(self.hours_value)
        layout.add_widget(self.hours_slider)
        self.add_widget(layout)

    def on_value_hours(self, instance, slider):
        self.hours_value.text = "%d"%slider
        print(instance)
        print("%d"%slider)
        return slider

class myapp(MDApp):
    def build(self):
        self.theme_cls = ThemeManager()
        self.theme_cls.primary_palette = 'Orange'
        self.theme_cls.accent_pallete = 'Blue'
        self.theme_cls.theme_style = 'Dark'

        sm = ScreenManager()
        sm.add_widget(Screen1(name = 's1'))
        return sm

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

但是现在我想在我的函数def on_value_hours(self, instance, slider):之外的滑块上获得价值

所以我添加此代码my_value_slider = on_value_hours()

但我收到一个错误 on_value_hours() 缺少 3 个必需的位置参数：“self”、“instance”和“slider”

我尝试添加my_value_slider = on_value_hours(1,1,1)

但这对我也不起作用:(

给我一​​个错误AttributeError: 'int' object has no attribute 'hours_value'

这是一个完整的代码，但仍然给我一个错误。我想在我的职能之外获得价值。请帮帮我。

from kivy.uix.screenmanager import ScreenManager, Screen
from kivy.uix.floatlayout import FloatLayout
from kivymd.app import MDApp
from kivymd.theming import ThemeManager
from kivymd.uix.slider import Slider
from kivy.properties  import NumericProperty
from kivymd.uix.label import MDLabel

class Screen1(Screen):
    def __init__(self, **kwargs):
        super(Screen1, self).__init__(**kwargs)
        layout = FloatLayout()

        self.hours_value = MDLabel(text = "0", halign = "center", pos_hint = 'center_x':.5, 'center_y':.80, theme_text_color = 'Error')
        self.hours_slider = Slider(min = 0, max = 24, pos_hint = 'center_x':.5, size_hint_x = .7)
        self.hours_slider.bind(value = self.on_value_hours)

        layout.add_widget(self.hours_value)
        layout.add_widget(self.hours_slider)
        self.add_widget(layout)

    def on_value_hours(self, instance, slider):
        self.hours_value.text = "%d"%slider
        print(instance)
        print("%d"%slider)
        return slider

    my_value_slider = on_value_hours(1,1,1)

class myapp(MDApp):
    def build(self):
        self.theme_cls = ThemeManager()
        self.theme_cls.primary_palette = 'Orange'
        self.theme_cls.accent_pallete = 'Blue'
        self.theme_cls.theme_style = 'Dark'

        sm = ScreenManager()
        sm.add_widget(Screen1(name = 's1'))
        return sm

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

【参考方案1】：

你可以这样做：

class Screen1(Screen):
    # slider value
    my_value_slider = NumericProperty(0)

    def __init__(self, **kwargs):
        super(Screen1, self).__init__(**kwargs)
        layout = FloatLayout()

        self.hours_value = MDLabel(text = "0", halign = "center", pos_hint = 'center_x':.5, 'center_y':.80, theme_text_color = 'Error')
        self.hours_slider = Slider(min = 0, max = 24, pos_hint = 'center_x':.5, size_hint_x = .7)
        self.hours_slider.bind(value = self.on_value_hours)

        layout.add_widget(self.hours_value)
        layout.add_widget(self.hours_slider)
        self.add_widget(layout)

    def on_value_hours(self, instance, slider):
        self.hours_value.text = "%d"%slider
        print(instance)
        print("%d"%slider)

        # save value
        self.my_value_slider = slider
        return slider

【讨论】：

非常感谢！这对我有用 :) 你是神

这很好，但只能在这个类中使用，如何使它成为另一个类的访问权限？

您可以通过对Screen1 的引用来做到这一点，这可以从您的ScreenManager 获得。

如果我输入另一个类 s = Screen1() the_value = s.my_value_slider print(the_value) 这给我一个 0 值

是的，因为这不是访问变量的正确方法。代码s = Screen1() 创建Screen1 的新实例，并且不引用GUI 中的实例。你应该可以做类似App.get_running_app().root.get_screen('s1').my_value_slider的事情。

【参考方案2】：

另一种方法更像是您的初始代码，其中my_slider_value 将是一个类变量（而不是实例变量）：

class Screen1(Screen):
    # class variable
    my_value_slider = 0

    def __init__(self, **kwargs):
        super(Screen1, self).__init__(**kwargs)
        layout = FloatLayout()

        self.hours_value = MDLabel(text = "0", halign = "center", pos_hint = 'center_x':.5, 'center_y':.80, theme_text_color = 'Error')
        self.hours_slider = Slider(min = 0, max = 24, pos_hint = 'center_x':.5, size_hint_x = .7)
        self.hours_slider.bind(value = self.on_value_hours)

        layout.add_widget(self.hours_value)
        layout.add_widget(self.hours_slider)
        self.add_widget(layout)

    def on_value_hours(self, instance, slider):
        self.hours_value.text = "%d"%slider
        print(instance)
        print("%d"%slider)

        # update value of class variable
        Screen1.my_value_slider = slider

        return slider

然后您可以以Screen1.my_value_slider 的身份访问my_value_slider。请注意，在该访问中没有使用括号。这种方式的缺点是my_value_slider不是Property，所以不能绑定到它。