如何解决错误“ Nonetype对象没有属性'bind'”？

用户名

我刚开始用kivy创建一个新应用，而当尝试从应用类中调用StringProperty kujund时，我根本不明白为什么它给我一个错误。

蟒蛇：

from kivy.app import App
from kivy.lang import Builder
from kivy.uix.screenmanager import ScreenManager, Screen
from kivy.properties import StringProperty
from kivy.clock import Clock

kv = Builder.load_file("autogeo.kv")
kujund = "null"

class autogeo(App):
    manager = ScreenManager()

    Screen1 = Screen(name="esimene")
    Screen2 = Screen(name='teine')
    Screen3 = Screen(name="kolmas")
    Screen4 = Screen(name='neljas')
    Screen5 = Screen(name="viies")
    kujund = StringProperty()

    def update(self, *args):
        pass
    def build(self):
        Clock.schedule_interval(self.update, 0.1)
        return kv

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

Kv：

ScreenManager:
    id: manager
    size: root.width, root.height

    Screen:
        name: "esimene"
        GridLayout:
            cols: 2
            rows: 3
            Button:
                text: "ruut"
                on_press:
                    manager.current = "teine"
                    manager.transition.direction ="left"
                    app.kujund: "ruut"

            Button:
                text: "ristkylik"
                on_press:
                    manager.current = "teine"
                    manager.transition.direction ="left"
            Button:
                text: "kolmnurk"
                on_press:
                    manager.current = "teine"
                    manager.transition.direction ="left"
            Button:
                text: "taisnurkne kolmnurk"
                on_press:
                    manager.current = "teine"
                    manager.transition.direction ="left"
            Button:
                text: "ring"
                on_press:
                    manager.current = "teine"
                    manager.transition.direction ="left"
            Button:
                text: "vordhaarne trapets"
                on_press:
                    manager.current = "teine"
                    manager.transition.direction ="left"
    Screen:
        name: "teine"
        FloatLayout:
            Label:
                text: "Valisid kujundi " + app.kujund
                font_size: self.width * 0.1
            Button:
                text: "tagasi"
                size_hint: 1, 0.2
                on_press:
                    manager.current = "esimene"
                    manager.transition.direction = "right"

追溯：

 Traceback (most recent call last):
   File "C:\Users\ricsi\Anaconda3\lib\site-packages\kivy\lang\builder.py", line 249, in create_handler
     return eval(value, idmap), bound_list
   File "C:\Users\ricsi\PycharmProjects\ToolsforMaths\autogeo.kv", line 46, in <module>
     text: "Valisid kujundi " + app.kujund
   File "C:\Users\ricsi\Anaconda3\lib\site-packages\kivy\lang\parser.py", line 75, in __getattribute__
     object.__getattribute__(self, '_ensure_app')()
   File "C:\Users\ricsi\Anaconda3\lib\site-packages\kivy\lang\parser.py", line 70, in _ensure_app
     app.bind(on_stop=lambda instance:
 AttributeError: 'NoneType' object has no attribute 'bind'

永乐

在创建“ app”之前，您正在加载使用“ app”的.kv，因此没有错误引发该错误。解决方案是在创建“ app”（例如构建方法）之后对其进行解析。

from kivy.app import App
from kivy.lang import Builder
from kivy.uix.screenmanager import ScreenManager, Screen
from kivy.properties import StringProperty
from kivy.clock import Clock


class autogeo(App):
    manager = ScreenManager()

    Screen1 = Screen(name="esimene")
    Screen2 = Screen(name="teine")
    Screen3 = Screen(name="kolmas")
    Screen4 = Screen(name="neljas")
    Screen5 = Screen(name="viies")
    kujund = StringProperty()

    def update(self, *args):
        pass

    def build(self):
        kv = Builder.load_file("autogeo.kv")
        Clock.schedule_interval(self.update, 0.1)
        return kv


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

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