为什么更改字体后字体大小不立即更改？

Question

我正在尝试在更改标签字体大小的设置中创建一个选项。

我尝试使用属性，以便当用户在设置中更改字体大小时，结果/更改将立即显示。相反，更改仅在重新启动应用程序时生效。这是我的代码供参考。

example.py

import kivy
from kivy.properties import *
from kivy.uix.settings import SettingsWithSidebar
from kivy.uix.label import Label
from kivy.config import ConfigParser
from kivy.app import App

example_config = ConfigParser()
example_config.read("example.ini")


class TitleLabel(Label):
    font_size = ConfigParserProperty(defaultvalue=40, section="style", key="font_size",
                                     config=example_config, rebind=True)


class ExampleApp(App):

    def build(self):
        self.settings_cls = SettingsWithSidebar
        self.use_kivy_settings = False

    def build_config(self, config):
        config.setdefaults(
            "style", {"font_size": 40}
        )

    def build_settings(self, settings):
        settings.add_json_panel("Settings", self.config, "settings.json")


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

example.kv

FloatLayout:

    TitleLabel:
    SettingsButton:


<TitleLabel>:
    text: "[color=#30C9E9]ExampleTitleText[/color]"

    markup: True
    font_size: int(root.font_size)
    size_hint: None, None
    size: self.texture_size
    pos_hint: {"center_x": 0.5, "center_y": 0.5}

<SettingsButton@Button>:
    text: "Settings"
    size_hint: 0.1, 0.1
    pos_hint: {"right": 0.975, "top": 0.975}
    on_release: app.open_settings()

settings.ini

[
  {
    "type": "numeric",
    "title": "Font Size",
    "desc": "Pick how big you want the font to be.",
    "section": "style",
    "key": "font_size"
  }
]

我尝试将ConfigParserProperty() 链接到font_size（在example.kv 下<TitleLabel>）。我也尝试将NumericProperty(example_config.get("style", "font_size")) 链接到font_size。都没有奏效。我知道它必须与 properties 相关，但我不知道如何设置它。

如果您知道如何解决此问题，我们将非常感谢您的帮助。

Answer 1

kivy 团队有一个例子就是这样做的。 我认为其中重要的是他们用来更新所有修改值的 on_config_change 方法 - 希望它有所帮助

"""
Config Example
==============

This file contains a simple example of how the use the Kivy settings classes in
a real app. It allows the user to change the caption and font_size of the label
and stores these changes.

When the user next runs the programs, their changes are restored.

"""

from kivy.app import App
from kivy.uix.settings import SettingsWithTabbedPanel
from kivy.logger import Logger
from kivy.lang import Builder

# We first define our GUI
kv = '''
BoxLayout:
    orientation: 'vertical'
    Button:
        text: 'Configure app (or press F1)'
        on_release: app.open_settings()
    Label:
        id: label
        text: 'Hello'
'''

# This JSON defines entries we want to appear in our App configuration screen
json = '''
[
    {
        "type": "string",
        "title": "Label caption",
        "desc": "Choose the text that appears in the label",
        "section": "My Label",
        "key": "text"
    },
    {
        "type": "numeric",
        "title": "Label font size",
        "desc": "Choose the font size the label",
        "section": "My Label",
        "key": "font_size"
    }
]
'''


class MyApp(App):
    def build(self):
        """
        Build and return the root widget.
        """
        # The line below is optional. You could leave it out or use one of the
        # standard options, such as SettingsWithSidebar, SettingsWithSpinner
        # etc.
        self.settings_cls = MySettingsWithTabbedPanel

        # We apply the saved configuration settings or the defaults
        root = Builder.load_string(kv)
        label = root.ids.label
        label.text = self.config.get('My Label', 'text')
        label.font_size = float(self.config.get('My Label', 'font_size'))
        return root

    def build_config(self, config):
        """
        Set the default values for the configs sections.
        """
        config.setdefaults('My Label', {'text': 'Hello', 'font_size': 20})

    def build_settings(self, settings):
        """
        Add our custom section to the default configuration object.
        """
        # We use the string defined above for our JSON, but it could also be
        # loaded from a file as follows:
        #     settings.add_json_panel('My Label', self.config, 'settings.json')
        settings.add_json_panel('My Label', self.config, data=json)

    def on_config_change(self, config, section, key, value):
        """
        Respond to changes in the configuration.
        """
        Logger.info("main.py: App.on_config_change: {0}, {1}, {2}, {3}".format(
            config, section, key, value))

        if section == "My Label":
            if key == "text":
                self.root.ids.label.text = value
            elif key == 'font_size':
                self.root.ids.label.font_size = float(value)

    def close_settings(self, settings=None):
        """
        The settings panel has been closed.
        """
        Logger.info("main.py: App.close_settings: {0}".format(settings))
        super(MyApp, self).close_settings(settings)


class MySettingsWithTabbedPanel(SettingsWithTabbedPanel):
    """
    It is not usually necessary to create subclass of a settings panel. There
    are many built-in types that you can use out of the box
    (SettingsWithSidebar, SettingsWithSpinner etc.).

    You would only want to create a Settings subclass like this if you want to
    change the behavior or appearance of an existing Settings class.
    """
    def on_close(self):
        Logger.info("main.py: MySettingsWithTabbedPanel.on_close")

    def on_config_change(self, config, section, key, value):
        Logger.info(
            "main.py: MySettingsWithTabbedPanel.on_config_change: "
            "{0}, {1}, {2}, {3}".format(config, section, key, value))


MyApp().run()