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<HomeScreen>:     BoxLayout:         orientation: "vertical"          MDToolbar:             title: "Home"             md_bg_color: app.theme_cls.primary_color             left_action_items: [["menu", lambda x: app.root.toggle_nav_drawer()]]          MDBottomNavigation:             panel_color: rgba(180, 187, 114, 255)             text_color_active: rgba(246, 250, 247, 255)              MDBottomNavigationItem:                 name: "screen 1"                 text: "Records"                 font_name: "Poppins-Medium"                 icon: "leaf"                 icon_color: rgba(231, 234, 168, 255)                 MDLabel:                     text: "Here is chats!"                     halign: "center"              MDBottomNavigationItem:                 name: "screen 2"                 text: "Scan"                 font_name: "Poppins-Medium"                 icon: "image-plus"                 MDLabel:                     text: "Here is coffee!"                     font_name: "Poppins-Medium"                     halign: "center"             MDBottomNavigationItem:                 name: "screen 3"                 text: "Settings"                 font_name: "Poppins-Medium"                 icon: "cog"                 MDLabel:                     text: "Here is python!"                     font_name: "Poppins-Medium"                     halign: "center"             MDBottomNavigationItem:                 name: "screen 4"                 text: "About"                 font_name: "Poppins-Medium"                 icon: "information"                 MDLabel:                     text: "Here is Python!"                     halign: "center"

from kivy.core.text import LabelBase from kivy.uix.screenmanager import ScreenManager, Screen from kivymd.app import MDApp from kivy.lang import Builder from kivy.core.window import Window # 移除不必要的导入，例如 FakeRectangularElevationBehavior, get_color_from_hex, requests # 如果这些在其他地方未使用，可以删除以保持代码整洁。 # from kivymd.uix.floatlayout import MDFloatLayout # 如果login/signup kv文件需要，保留  Window.size = (310, 580)  # HomeScreen 类，其内容将由 home.kv 定义 class HomeScreen(Screen):     pass  class Myapp(MDApp):     def build(self):         # 设置应用主题颜色（可选）         self.theme_cls.primary_palette = "Green" # 示例          screen_manager = ScreenManager()          # 加载并添加所有屏幕的KV文件         # 注意：Builder.load_file() 会返回KV文件中定义的根组件。         # 如果KV文件的根是MDScreen或Screen，则可以直接添加到ScreenManager。         screen_manager.add_widget(Builder.load_file("start.kv"))         screen_manager.add_widget(Builder.load_file("signup.kv"))         screen_manager.add_widget(Builder.load_file("login.kv"))          # 对于 HomeScreen，由于 home.kv 的根规则是 <HomeScreen>，         # Kivy 会在实例化 HomeScreen 时自动应用 home.kv 的规则。         home_screen = HomeScreen(name="home")         screen_manager.add_widget(home_screen)          # 设置应用的初始屏幕         screen_manager.current = "main" # 假设 "main" 是启动页面的名称          return screen_manager      # 移除或根据需要修改未使用的 change_color 方法     # def change_color(self, instance):     #     if instance in self.root.ids.values():     #         current_id = list(self.root.ids.keys())[list(self.root.ids.values()).index(instance)]     #         for i in range(4):     #             if f"nav_icon{i}" == current_id:     #                 self.root.ids[f"nav_icon{i + 1}"].text_color = 1, 0, 0, 1     #             else:     #                 self.root.ids[f"nav_icon{i + 1}"].text_color = 0, 0, 0, 1      # 如果 login.kv 中的 on_release 已经直接使用 root.manager.current = "home"，     # 那么 goto_home_screen 方法可能不再需要，或者可以用于更复杂的逻辑。     # def goto_home_screen(self):     #     self.root.current = "home"  if __name__ == "__main__":     # 确保字体路径正确     LabelBase.register(name="Poppins-Medium", fn_regular=r"C:UsersUserDesktopFONTPoppinsPoppins-Medium.ttf")     LabelBase.register(name="Poppins-SemiBold", fn_regular=r"C:UsersUserDesktopFONTPoppinsPoppins-SemiBold.ttf")      # 移除对未定义 NavBarScreen 的注册     # Factory.register("NavBarScreen", cls=NavBarScreen)     Myapp().run()