如何单独控制Kivy设置面板中菜单项的字体大小？

当全局设置<Label>: font_size:50时，Kivy的SettingsWithTabbedPanel面板内的标签、选项组名称等基于Label的控件会继承该全局样式，导致界面显示异常。

方案1：用KV精准选择器控制样式范围 #

无需自定义Label子类，通过Widget层级选择器，仅对应用内需要的Label设置大字体，让Settings面板内的Label保持默认样式。

修改scattertest.kv：

#:kivy 2.1.0

<SquareWidget>: 
    size: 100, 100
    canvas: 
        Color: 
            rgb: [0.345, 0.85, 0.456] 
        Rectangle: 
            size: self.size 
            pos: self.pos 

<ScatterTest>:
    canvas: 
        Color: 
            rgb: .8, .5, .4
        Rectangle: 
            size: self.size 
            pos: self.pos   

    ScatterWidget: 
        id: square_widget_id  
   
        SquareWidget: 

    # 直接给目标Label设置字体，而非全局覆盖
    Label:
        font_size:50
        text: 'Position: ' + str(square_widget_id.pos) 
        size_hint: .1, .1
        pos: 500, 300

# 若需多个大字体Label，可自定义规则而非全局Label
<CustomBigLabel@Label>:
    font_size:50
# 后续在需要的地方替换为<CustomBigLabel>即可

如果必须保留全局样式但排除Settings面板，可针对Settings相关控件的子Label重置字体：

# 重置SettingsWithTabbedPanel内所有Label的字体大小
<SettingsWithTabbedPanel>:
    Label:
        font_size: 14  # 设为默认字体大小

# 单独修正TabbedPanel的标签字体
<TabbedPanelItem>:
    Label:
        font_size: 14

方案2：自定义Settings类重写内部样式 #

继承SettingsWithTabbedPanel，在Python代码中修改其内部控件的字体大小：

import kivy 
from kivy.app import App
kivy.require('1.9.0')  
from kivy.uix.scatter import Scatter 
from kivy.uix.widget import Widget
from kivy.uix.relativelayout import RelativeLayout 
from kivy.uix.settings import SettingsWithTabbedPanel
from kivy.logger import Logger
from kivy.uix.label import Label

class CustomSettingsPanel(SettingsWithTabbedPanel):
    def __init__(self, **kwargs):
        super().__init__(**kwargs)
        # 修改标签页的字体
        for tab in self.tabbed_panel.tab_list:
            if isinstance(tab.text_label, Label):
                tab.text_label.font_size = 14
        # 修改选项组标题的字体
        for section in self.interface.children:
            if hasattr(section, 'title') and isinstance(section.title, Label):
                section.title.font_size = 14

class SquareWidget(Widget): 
    pass

class ScatterWidget(Scatter): 
    pass

class ScatterTest(RelativeLayout): 
    pass

class ScatterTestApp(App): 
    def build(self):                
        self.settings_cls = CustomSettingsPanel
        return ScatterTest()

    def app_open_settings(self):
        App.open_settings(self)

    def close_settings(self, settings=None):
        Logger.info("scattertest.py: App.close_settings: {0}".format(settings))
        super(ScatterTestApp, self).close_settings(settings)

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

方案3：用Style类管理全局样式 #

通过Kivy的样式管理，为应用内Label和Settings面板Label设置不同规则：

from kivy.core.window import Window
from kivy.uix.label import Label

def apply_styles():
    # 给主窗口内的Label设置大字体
    for widget in Window.children[0].walk():
        if isinstance(widget, Label) and not hasattr(widget, '_is_settings_label'):
            widget.font_size = 50
    
    # 标记并重置Settings面板内的Label字体
    def mark_settings_labels(settings):
        for widget in settings.walk():
            if isinstance(widget, Label):
                widget._is_settings_label = True
                widget.font_size = 14

    # 替换默认的打开设置方法，添加样式修正
    original_open = App.open_settings
    def custom_open_settings(self):
        settings = original_open(self)
        mark_settings_labels(settings)
        return settings
    App.open_settings = custom_open_settings

# 在App的build方法中调用
class ScatterTestApp(App): 
    def build(self):                
        apply_styles()
        self.settings_cls = SettingsWithTabbedPanel
        return ScatterTest()

• 方案1最简洁，通过KV选择器精准控制样式范围，避免全局污染；
• 方案2适合需要深度定制Settings面板的场景；
• 方案3适配复杂的全局样式管理需求。

内容的提问来源于stack exchange，提问作者phchen2