Kivy，python：如何从根类（FaceRecApp）访问外部/子类？
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【中文标题】Kivy，python：如何从根类（FaceRecApp）访问外部/子类？【英文标题】：Kivy, python: how to access to an external/child class from the root class (FaceRecApp)? 【发布时间】：2017-09-13 00:36:18 【问题描述】：如何使用 python 或 kivy 访问另一个类的标签/id 并避免下面的错误？ 我在其他帖子中进行了搜索，发现无法通过根类引用另一个类......但是，我不知道有任何其他方法可以做到这一点。我希望你能帮助我。 提前致谢。
FaceRec.py
图书馆
from kivy.app import App
from kivy.uix.screenmanager import ScreenManager,Screen
from kivy.uix.widget import Widget
from kivy.uix.label import Label
from kivy.uix.settings import SettingsWithSidebar
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.actionbar import ActionBar
from kivy.logger import Logger
from kivy.config import Config
设置屏幕尺寸
Config.set('graphics', 'width', '850')
Config.set('graphics', 'height', '850')
HomeScreen 类
class ScreenManagement(ScreenManager):
pass
class HomeScreen(Screen):
pass
class HomeActionBar(ActionBar):
pass
class TitleLabel(Label):
pass
class StatusBoxLayout(BoxLayout):
pass
class ErrorsBoxLayout(BoxLayout):
pass
主类
class FaceRecApp(App):
def build(self):
root = HomeScreen()
Logger.info('FaceRec.py: FaceRec.kv loaded')
self.settings_cls = MySettingsWithSidebar
Logger.info('FaceRec.py: MySettingsWithSidebar loaded')
status = root.ids.StatusBoxLayout.status
status.font_size = float(self.config.get('General', 'font_size'))
label = root.ids.label
label.font_size = float(self.config.get('General', 'font_size'))
return root
def build_config(self, config):
config.setdefaults('General', 'text': 'Default Hello','font_size': 20)
def build_settings(self, settings):
settings.add_json_panel('General', self.config, 'Settings.json')
def on_config_change(self, config, section, key, value):
Logger.info("FaceRec.py: App.on_config_change: 0, 1, 2, 3".format(config, section, key, value))
if section == "General":
if key == "text":
self.root.ids.label.text = value
elif key == 'font_size':
self.root.ids.label.font_size = float(value)
self.root.ids.StatusBoxLayout.status = float(value)
def close_settings(self, settings):
Logger.info("FaceRec.py: App.close_settings: 0".format(settings))
super(FaceRecApp, self).close_settings(settings)
侧边栏设置
class MySettingsWithSidebar(SettingsWithSidebar):
def on_close(self):
Logger.info('FaceRec.py: MySettingsWithSidebar.on_close')
def on_config_change(self, config, section, key, value):
Logger.info(
"FaceRec.py: MySettingsWithSidebar.on_config_change: "
"0, 1, 2, 3".format(config, section, key, value))
执行
if __name__ == '__main__':
FaceRecApp().run()
FaceRec.kv
ScreenManagement:
HomeScreen:
<HomeActionBar>:
id: HomeActionBar
pos_hint: 'bottom':0
ActionView:
use_separator: True
ActionPrevious:
title: 'Home'
with_previous: False
ActionOverflow:
ActionButton:
text: 'Settings'
icon: 'settings.png'
background_down: 'settings.png'
on_release:
app.open_settings()
<TitleLabel>:
id: TitleLabel
text: '[b]FaceRec[/b] - [i]The Face Recognition Project[/i]'
color: 0.0,0.3,1,1
markup: True
font_size: 38
<StatusBoxLayout>:
orientation: 'horizontal'
#padding: 100
Label:
id: status
text: 'Status: '
font_size: 20
Label:
id: status_value
text: 'Error'
font_size: 20
color: 1,0,0,1
<ErrorsBoxLayout>:
id: ErrorsBoxLayout
orientation: 'horizontal'
#padding: 100
Label:
id: errors
text: 'Errors No: '
font_size: 20
Label:
id: errors_value
text: '...'
font_size: 20
<HomeScreen>:
id: HomeScreen
BoxLayout:
orientation: 'vertical'
HomeActionBar:
TitleLabel:
BoxLayout:
cols: 2
orientation: 'vertical'
StatusBoxLayout:
ErrorsBoxLayout:
Label:
id: label
text: 'Does it run?'
Settings.json
[
"type": "string",
"title": "Label caption",
"desc": "Choose the text that appears in the label",
"section": "General",
"key": "text"
,
"type": "numeric",
"title": "Label font size",
"desc": "Choose the font size the label",
"section": "General",
"key": "font_size"
]
我尝试访问 label 变量（FaceRecApp、build 和 on_config_change 函数）并且程序运行正常。当我在设置中更改标签的字体大小时，更改已应用到 HomeScreen。然后我添加了以下代码行：
在构建（）中：
status = root.ids.StatusBoxLayout.status
status.font_size = float(self.config.get('General', 'font_size'))
在 on_config_change() 中：
self.root.ids.StatusBoxLayout.status = float(value)
结果一直出错：
[INFO ] [Logger ] Record log in C:\***\.kivy\logs\kivy_17-04-17_109.txt
[INFO ] [Kivy ] v1.9.1
[INFO ] [Python ] v2.7.13 (v2.7.13:a06454b1afa1, Dec 17 2016, 20:53:40) [MSC v.1500 64 bit (AMD64)]
[INFO ] [Factory ] 179 symbols loaded
[INFO ] [Image ] Providers: img_tex, img_dds, img_gif, img_sdl2, img_pil (img_ffpyplayer ignored)
[INFO ] [Text ] Provider: sdl2
[INFO ] [OSC ] using <thread> for socket
[INFO ] [Window ] Provider: sdl2
[INFO ] [GL ] GLEW initialization succeeded
[INFO ] [GL ] OpenGL version <4.5.0 NVIDIA 376.53>
[INFO ] [GL ] OpenGL vendor <NVIDIA Corporation>
[INFO ] [GL ] OpenGL renderer <GeForce ***/PCIe/SSE2>
[INFO ] [GL ] OpenGL parsed version: 4, 5
[INFO ] [GL ] Shading version <4.50 NVIDIA>
[INFO ] [GL ] Texture max size <16384>
[INFO ] [GL ] Texture max units <32>
[INFO ] [Window ] auto add sdl2 input provider
[INFO ] [Window ] virtual keyboard not allowed, single mode, not docked
[INFO ] [FaceRec.py ] FaceRec.kv loaded
[INFO ] [FaceRec.py ] MySettingsWithSidebar loaded
Traceback (most recent call last):
File "C:/***/PycharmProjects/face_recognition_2/FaceRec.py", line 114, in <module>
FaceRecApp().run()
File "C:\Python27\lib\site-packages\kivy\app.py", line 802, in run
root = self.build()
File "C:/***/PycharmProjects/face_recognition_2/FaceRec.py", line 65, in build
status = root.ids.StatusBoxLayout.status
File "kivy\properties.pyx", line 757, in kivy.properties.ObservableDict.__getattr__ (kivy\properties.c:11882)
AttributeError: 'super' object has no attribute '__getattr__'
Process finished with exit code 1
我已经阅读了这篇文章（以及许多其他文章......）： How to access id/widget of different class from a kivy file (.kv)? 但我的程序还没有运行。
再次感谢您的支持。
【问题讨论】：
【参考方案1】：您忘记在根类 (HomeScreen) 中为 StatusBoxLayout 提供 id。 id 需要在根类中给出，以便能够将其作为 self.root.ids.StatusBoxLayout 访问。 所以在 HomeScreen 中给它它的 id：
<HomeScreen>:
id: HomeScreen
BoxLayout:
orientation: 'vertical'
HomeActionBar:
TitleLabel:
BoxLayout:
cols: 2
orientation: 'vertical'
StatusBoxLayout:
id: StatusBoxLayout
ErrorsBoxLayout:
id: ErrorsBoxLayout
当您使用它时，您不妨也给ErrorsBoxLayout 一个 id，或者您需要通过 id 访问的任何其他类。
现在当您分配 status = root.ids.StatusBoxLayout.status 时，改为这样分配：
status = self.root.ids.StatusBoxLayout.ids.status
您需要在前面加上self，因为稍后在您的App 课程中，您想要获取或设置self.root。但是您没有将root 定义为类属性。
而第二个 ids 是因为 status 是 StatusBoxLayout 的 id
所以你的构建方法应该是这样的：
def build(self):
self.root = HomeScreen()
Logger.info('FaceRec.py: FaceRec.kv loaded')
self.settings_cls = MySettingsWithSidebar
Logger.info('FaceRec.py: MySettingsWithSidebar loaded')
status = self.root.ids.StatusBoxLayout.ids.status
status.font_size = float(self.config.get('General', 'font_size'))
label = self.root.ids.label
label.font_size = float(self.config.get('General', 'font_size'))
return self.root
【讨论】：
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