加载时更新 kivy 中的标签文本

Question

我是 kivy 的新手，正在尝试为我的树莓派构建小型 OSD。

我的 .kv 文件如下所示：

BoxLayout:
    orientation: 'vertical'
    Label:
        text_size: self.size
        text: 'OSD'
        font_size: 50
        bold: True
        halign: 'center'
        valign: 'top'
        size_hint: 1, .3
    GridLayout:
        cols: 2
        Label:
            text_size: self.size
            text: 'Total entries in DB: '
            font_size: 30
            bold: False
            halign:  'left'
            size_hint: 1, .1
        Label:
            id: total_db
            text_size: self.size
            text: '366 000 '
            font_size: 30
            bold: True
            color: 0, 1, 0, 1
            halign:  'center'
            size_hint: 1, .1
        Label:
            text_size: self.size
            text: 'Info 1: '
            font_size: 30
            bold: False
            halign: 'left'
            size_hint: 1, .1
        Label:
            id: marked_update
            text_size: self.size
            text: '1328 '
            color: 1, 0, 0, 1
            font_size: 30
            bold: True
            halign:  'center'
            size_hint: 1, .1
    Label:
        text_size: self.size
        text: 'Activity'
        font_size: 50
        bold: True
        halign: 'center'
        valign: 'top'
        size_hint: 1, .3
    Label:
        text: ''
        font_size: 10
        halign: 'center'
        valign: 'top'
        size_hint: 1, .08

    GridLayout:
        cols: 4
        Button:
            text: 'DS 01'
            font_size: 25
            background_color: 1, 0, 0, 1
        Button:
            text: 'DS 02'
            font_size: 25
            background_color: 0, 1, 0, 1
        Button:
            text: 'DS 03'
            font_size: 25
            background_color: 0, 1, 0, 1
        Button:
            text: 'DS 04'
            font_size: 25
            background_color: 0, 1, 0, 1

这会产生我想要的外观。我想定期更新带有 ID 的两个标签文本以及我稍后提取的值...但我什至无法从 python 更新它们，如下所示：

import kivy
kivy.require('1.10.1')

from kivy.app import App
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.label import Label
from kivy.clock import Clock

class BoxLayout(BoxLayout):
    def __init__(self, **kwargs):
        super(BoxLayout, self).__init__(**kwargs)
        Clock.schedule_once(self.update_txt, 0)

    def update_txt(self, *args):
        self.label.ids.marked_update.txt='updated from python'

class osdApp(App):
    def build(self):
        self.title = 'OSD'
        return BoxLayout()


if __name__ == '__main__':
    osdApp().run()

我正在考虑启动调用 update_txt 函数的时钟，这可能会改变值，但我一直收到错误，ids 不存在......等等，我是新手面向对象编程，我搞不懂这个简单的事情

Answer 1

几点观察：

正如@eyllanesc 的评论，你不应该将你的子 class 命名为它继承的 class。
self.label.ids.marked_update.txt 不正确。应该是self.ids.marked_update.text.
将您的根小部件声明为 kv 规则。

您的代码可以是：

main.py

import kivy
kivy.require('1.10.0')

from kivy.app import App
from kivy.uix.boxlayout import BoxLayout
from kivy.clock import Clock


class RootWidget(BoxLayout):

    def __init__(self, **kwargs):
        super(BoxLayout, self).__init__(**kwargs)
        Clock.schedule_once(self.update_txt, 0.1)

    def update_txt(self, *args):
        self.ids.marked_update.text = 'updated from python'


class OsdApp(App):
    def build(self):
        self.title = 'OSD'
        return RootWidget()


if __name__ == '__main__':
    OsdApp().run()

osd.kv:

<RootWidget>:
    orientation: 'vertical'
    Label:
        text_size: self.size
        text: 'OSD'
        font_size: 50
        bold: True
        halign: 'center'
        valign: 'top'
        size_hint: 1, .3
    GridLayout:
        cols: 2
        Label:
            text_size: self.size
            text: 'Total entries in DB: '
            font_size: 30
            bold: False
            halign:  'left'
            size_hint: 1, .1
        Label:
            id: total_db
            text_size: self.size
            text: '366 000 '
            font_size: 30
            bold: True
            color: 0, 1, 0, 1
            halign:  'center'
            size_hint: 1, .1
        Label:
            text_size: self.size
            text: 'Info 1: '
            font_size: 30
            bold: False
            halign: 'left'
            size_hint: 1, .1
        Label:
            id: marked_update
            text_size: self.size
            text: '1328 '
            color: 1, 0, 0, 1
            font_size: 30
            bold: True
            halign:  'center'
            size_hint: 1, .1
    Label:
        text_size: self.size
        text: 'Activity'
        font_size: 50
        bold: True
        halign: 'center'
        valign: 'top'
        size_hint: 1, .3
    Label:
        text: ''
        font_size: 10
        halign: 'center'
        valign: 'top'
        size_hint: 1, .08

    GridLayout:
        cols: 4
        Button:
            text: 'DS 01'
            font_size: 25
            background_color: 1, 0, 0, 1
        Button:
            text: 'DS 02'
            font_size: 25
            background_color: 0, 1, 0, 1
        Button:
            text: 'DS 03'
            font_size: 25
            background_color: 0, 1, 0, 1
        Button:
            text: 'DS 04'
            font_size: 25
            background_color: 0, 1, 0, 1

但是，我建议使用 kivy 属性而不是 ids:

main.py:

import kivy
kivy.require('1.10.0')

from kivy.app import App
from kivy.uix.boxlayout import BoxLayout
from kivy.properties import StringProperty


class RootWidget(BoxLayout):
    marked_text = StringProperty()

    def __init__(self, **kwargs):
        super(BoxLayout, self).__init__(**kwargs)
        self.update_txt()

    def update_txt(self, *args):
        self.marked_text ='updated from python'


class OsdApp(App):
    def build(self):
        self.title = 'OSD'
        return RootWidget()


if __name__ == '__main__':
    OsdApp().run()

osd.kv:

<RootWidget>:
    id: root_layout
    orientation: 'vertical'
    marked_text: '1328 '

    Label:
        text_size: self.size
        text: 'OSD'
        font_size: 50
        bold: True
        halign: 'center'
        valign: 'top'
        size_hint: 1, .3
    GridLayout:
        cols: 2
        Label:
            text_size: self.size
            text: 'Total entries in DB: '
            font_size: 30
            bold: False
            halign:  'left'
            size_hint: 1, .1
        Label:
            id: total_db
            text_size: self.size
            text: '366 000 '
            font_size: 30
            bold: True
            color: 0, 1, 0, 1
            halign:  'center'
            size_hint: 1, .1
        Label:
            text_size: self.size
            text: 'Info 1: '
            font_size: 30
            bold: False
            halign: 'left'
            size_hint: 1, .1
        Label:
            id: marked_update
            text_size: self.size
            text: root_layout.marked_text
            color: 1, 0, 0, 1
            font_size: 30
            bold: True
            halign:  'center'
            size_hint: 1, .1
    Label:
        text_size: self.size
        text: 'Activity'
        font_size: 50
        bold: True
        halign: 'center'
        valign: 'top'
        size_hint: 1, .3
    Label:
        text: ''
        font_size: 10
        halign: 'center'
        valign: 'top'
        size_hint: 1, .08

    GridLayout:
        cols: 4
        Button:
            text: 'DS 01'
            font_size: 25
            background_color: 1, 0, 0, 1
        Button:
            text: 'DS 02'
            font_size: 25
            background_color: 0, 1, 0, 1
        Button:
            text: 'DS 03'
            font_size: 25
            background_color: 0, 1, 0, 1
        Button:
            text: 'DS 04'
            font_size: 25
            background_color: 0, 1, 0, 1

Answer 2

对于在 kivy 中搜索 on_load 事件而找到解决此问题方法的任何人，我已经找到了解决方案。 kivy 中的 App class 提供了一个成员函数 on_start(self)，一旦应用程序完成构建和加载就会调用它。我们只需要在应用程序完成加载后在其主体中添加我们想要调用的函数。例如：

class MyApp(App):
  def build(self):
    ...
  def on_start(self):
    super().on_start(self)
    my_f()
    update_texts()

加载时更新 kivy 中的标签文本

updating label text in kivy on load

python

kivy

kivy-language