如何在类方法初始化之前加载 Kivy ID(Python with K

问题描述

目标:成功初始化一个类方法(在我的例子中是 create_button())，该方法在 __init__ 的参数中引用了 kv id同一个类的方法.

Goal: Successfully initialize a class method (create_button(), in my case) that references kv ids in its parameter from the __init__ method of the same class.

我收到以下错误:

  File "C:/Users/phili/scrollablelabelexample.py", line 33, in __init__
    self.create_button(self.ids.box_share)

  File "kivyproperties.pyx", line 839, in kivy.properties.ObservableDict.__getattr__ (kivyproperties.c:12654)

AttributeError: 'super' object has no attribute '__getattr__'

怀疑:我相信这是因为我的 kv id 在类初始化之前没有加载

Suspicion: I believe it is because my kv ids are not loaded before class is initialized

问题:如何确保提前加载 kivy id?

我尝试过的事情:

1. 在代码前面构建 kv 文件
2. 使用时钟延迟create_button()的初始化
3. 使用@mainthread让ids先加载

1. Building kv file earlier in code
2. Use clock to delay initialization of create_button()
3. Using @mainthread to let ids load first

Python 代码:

from kivy.app import App
from kivy.lang import Builder
from kivy.uix.screenmanager import ScreenManager, Screen, FadeTransition
from kivy.uix.gridlayout import GridLayout
from kivy.uix.label import Label
from kivy.uix.widget import Widget
from kivy.uix.scrollview import ScrollView
from kivy.clock import Clock
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.button import Button

class AnotherScreen(Screen):
    pass

class Sequence(Screen):
    pass

class ScreenManagement(ScreenManager):
    pass

class MainScreen(Screen):
    pass

class CleanScreen(BoxLayout):
    def __init__(self, **kwargs):
        super(CleanScreen, self).__init__(**kwargs)
        self.orientation = "vertical"
        self.create_button(self.ids.box_share)

    def create_button(self, box_share):
        top_button_share = 1.1
        top_label_share = 1.4

        for i in range(50):
            top_button_share -= .4
            top_label_share -= .4

            button_share = Button(pos_hint={"x": 0, "top": top_button_share}, size_hint_y=None, height=40)
            label_share = Label(text=str(i), pos_hint={"x": 0, "top": top_label_share}, size_hint_y=None)

            box_share.add_widget(button_share)
            box_share.add_widget(label_share)

presentation = Builder.load_file("garagemainexample.kv")

class MainApp(App):
    def build(self):
        return presentation 

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

Kv代码:

#: import FadeTransition kivy.uix.screenmanager.FadeTransition

ScreenManagement:
    transition: FadeTransition()
    MainScreen:
    Sequence:

<BigButton@Button>:
    font_size: 40
    size_hint: 0.5, 0.15
    color: 0,1,0,1 

<SmallNavButton@Button>:    
    font_size: 32
    size: 125, 50    
    color: 0,1,0,1

<MainScreen>:
    name: "main"
    FloatLayout:
        BigButton:
            on_release: app.root.current = "sequence"
            text: "Sequence"
            pos_hint: {"x":0.25, "top": 0.4} 

<CleanScreen>:
    ScrollView:
        GridLayout:
            id: box_share
            cols: 1
            size_hint_y: None
            spacing: 10
            padding: 10
            height: self.minimum_height
            canvas:
                Color:
                    rgb: 1, 0, 1
                Rectangle:
                    pos: self.pos
                    size: self.size

<Sequence>:
    name: "sequence"
    CleanScreen:
        id: cleanscreen

推荐答案

小部件的子小部件的创建发生在父小部件的创建之后，在您的情况下，id 是在 CleanScreen 之后创建的.所以一个可能的解决方案是在构造函数用 Clock 调用后立即调用该方法:

The creation of the children of a widget occurs after the creation of the parent, in your case the ids are created after CleanScreen. So a possible solution is to call that method an instant after the constructor is called with Clock:

class CleanScreen(BoxLayout):
    def __init__(self, **kwargs):
        super(CleanScreen, self).__init__(**kwargs)
        self.orientation = "vertical"
        # You must call the method at the end of the constructor
        Clock.schedule_once(lambda *args:self.create_button(self.ids.box_share))

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