Kivy Scrollview：AttributeError：“NoneType”对象没有属性“绑定”
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【中文标题】Kivy Scrollview：AttributeError：“NoneType”对象没有属性“绑定”【英文标题】：Kivy Scrollview: AttributeError: 'NoneType' object has no attribute 'bind' 【发布时间】：2020-12-27 15:14:47 【问题描述】：早安，
我是这个网站的新手，但我经常控制有助于我编码的主题。我刚开始学习编码，我是 python 新手，我认为它是最好的之一。
顺便说一句：我正在使用 Kivy 构建一个由用户可以收集和查阅的卡片组成的应用程序。我制作了卡片（使用 MDCards），但屏幕被挡住了，如果我添加超过 5 张卡片，它们是不可见的（屏幕外）。我正在尝试在 KV 的 GridLayout 上添加滚动视图。遵循一些主题，我发现了这种方式。
from kivy.properties import ObjectProperty
from kivymd.app import MDApp
from kivy.lang import Builder
from kivy.uix.scrollview import ScrollView
from kivy.uix.floatlayout import FloatLayout
from kivy.core.window import Window
from kivy.uix.gridlayout import GridLayout
from kivy.app import runTouchApp
from kivy.uix.button import Button
KV = """
Screen:
Controller:
layout_content: layout_content
BoxLayout:
id: bl
orientation: 'vertical'
padding: 10, 10
row_default_height: '48dp'
row_force_default: True
spacing: 10, 10
ScrollView:
size: self.size
GridLayout:
id: layout_content
size_hint_y: None
cols: 1
row_default_height: '20dp'
row_force_default: True
spacing: 0, 0
padding: 0, 0
MDCard:
id: tel1
orientation: "vertical"
padding: "8dp"
size_hint: None, None
size: "180dp", "280dp"
pos_hint: "center_x": 0.5, "center_y": 0.5
MDLabel:
text: "Tele 1"
theme_text_color: "Secondary"
size_hint_y: None
height: self.texture_size[1]
MDSeparator:
height: "5dp"
width: "5dp"
MDLabel:
text: "Descrizione del primo"
MDCard:
id: tel2
orientation: "vertical"
padding: "8dp"
size_hint: None, None
size: "180dp", "280dp"
pos_hint: "center_x": 0.5, "center_y": 0.5
MDLabel:
text: "Tele 2"
theme_text_color: "Secondary"
size_hint_y: None
height: self.texture_size[1]
MDSeparator:
height: "5dp"
width: "5dp"
MDLabel:
text: "Descrizione del secondo"
MDCard:
id: tel2
orientation: "vertical"
padding: "8dp"
size_hint: None, None
size: "180dp", "280dp"
pos_hint: "center_x": 0.5, "center_y": 0.5
MDLabel:
text: "Tele 3"
theme_text_color: "Secondary"
size_hint_y: None
height: self.texture_size[1]
MDSeparator:
height: "5dp"
width: "5dp"
MDLabel:
text: "Descrizione del terzo"
MDCard:
id:tel4
orientation: "vertical"
padding: "8dp"
size_hint: None, None
size: "180dp", "280dp"
pos_hint: "center_x": 0.5, "center_y": 0.5
MDLabel:
text: "Telefilm 4"
theme_text_color: "Secondary"
size_hint_y: None
height: self.texture_size[1]
MDSeparator:
height: "5dp"
width: "5dp"
MDLabel:
text: "Descrizione del quarto"
MDCard:
id:tel5
orientation: "vertical"
padding: "8dp"
size_hint: None, None
size: "180dp", "280dp"
pos_hint: "center_x": 0.5, "center_y": 0.5
MDLabel:
text: "Tele 5"
theme_text_color: "Secondary"
size_hint_y: None
height: self.texture_size[1]
MDSeparator:
height: "5dp"
width: "5dp"
MDLabel:
text: "Descrizione del quinto"
"""
class Controller(FloatLayout):
layout_content = ObjectProperty(None)
def __init__(self, **kwargs):
super(Controller, self).__init__(**kwargs)
self.layout_content.bind(minimum_height=self.layout_content.setter('height'))
class MainApp(MDApp):
def build(self):
self.title = "LukeFlix"
self.theme_cls.theme_style = "Light"
self.theme_cls.primary_palette = "Red"
return Builder.load_string(KV)
MainApp().run()
但我收到此错误：
Traceback (most recent call last):
File "C:/Users/User/PycharmProjects/pythonProject3APP/main.py", line 140, in <module>
MainApp().run()
File "C:\Users\User\PycharmProjects\pythonProject3APP\venv\lib\site-packages\kivy\app.py", line 949, in run
self._run_prepare()
File "C:\Users\User\PycharmProjects\pythonProject3APP\venv\lib\site-packages\kivy\app.py", line 919, in _run_prepare
root = self.build()
File "C:/Users/User/PycharmProjects/pythonProject3APP/main.py", line 132, in build
return Builder.load_string(KV)
File "C:\Users\User\PycharmProjects\pythonProject3APP\venv\lib\site-packages\kivy\lang\builder.py", line 408, in load_string
self._apply_rule(
File "C:\Users\User\PycharmProjects\pythonProject3APP\venv\lib\site-packages\kivy\lang\builder.py", line 659, in _apply_rule
child = cls(__no_builder=True)
File "C:/Users/User/PycharmProjects/pythonProject3APP/main.py", line 125, in __init__
self.layout_content.bind(minimum_height=self.layout_content.setter('height'))
AttributeError: 'NoneType' object has no attribute 'bind'
Process finished with exit code 1
我该如何解决？
【问题讨论】：
【参考方案1】：该错误是由Controller 类的__init__() 方法引起的。此时，尚未分配 layout_content 属性。您可以通过像这样重新定义Controller 来消除__init__() 方法：
class Controller(FloatLayout):
pass
然后通过修改kv 的ScrollView 部分来实现相同的预期结果：
ScrollView:
# size: self.size # this has no effect
GridLayout:
id: layout_content
size_hint_y: None
cols: 1
# row_default_height: '20dp'
# row_force_default: True
height: self.minimum_height
spacing: 0, 0
padding: 0, 0
注意height: self.minimum_height 行，它执行您的__init__() 方法试图做的事情。此外，行默认值会强制GridLayout 中的行高度太小。
【讨论】：
伟大的@John Anderson。它奏效了，我都明白了。非常感谢！以上是关于Kivy Scrollview：AttributeError：“NoneType”对象没有属性“绑定”的主要内容，如果未能解决你的问题，请参考以下文章