如何在Python的Kivy框架中从另一个类修改Label文本？

修改后的Python代码 #

from kivy.app import App
from kivy.uix.screenmanager import ScreenManager, Screen
from kivy.lang import Builder
kv = Builder.load_file('test.kv')


class LessonsList(Screen):
    def press(self, lesson_num):
        # 获取LessonWindow页面实例
        lesson_screen = self.manager.get_screen('lesson')
        # 更新Label的文本内容
        lesson_screen.ids.lesson_label.text = f'Lesson {lesson_num}'
        # 切换到lesson页面
        self.manager.current = "lesson"


class LessonWindow(Screen):
    def back(self):
        self.manager.current = "lessons"
        self.manager.transition.direction = "left"


manager = ScreenManager()
manager.add_widget(LessonsList(name="lessons"))
manager.add_widget(LessonWindow(name="lesson"))


class MyApp(App):
    def build(self):
        return manager


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

修改后的kv文件 #

<LessonsList>:
    BoxLayout:
        size: root.width, root.height
        orientation: 'vertical'
        Button:
            text:'Lesson 1'
            on_press: root.press('1')
        Button:
            text:'Lesson 2'
            on_press: root.press('2')
        Button:
            text:'Lesson 3'
            on_press: root.press('3')

<LessonWindow>:
    BoxLayout:
        orientation: 'vertical'
        Label:
            id: lesson_label  # 添加id用于后续引用修改文本
            text: 'Lesson'
        Button:
            text:'Back'
            on_press: root.back()

关键改动说明 #

1. 给LessonsList的press方法添加lesson_num参数，用来接收点击按钮对应的课程编号
2. 在kv文件中，每个按钮调用press时传入对应的编号字符串
3. 给LessonWindow里的Label添加id，方便通过页面实例直接定位并修改文本
4. 修正back方法中直接使用manager的问题，改为self.manager（原代码会因未定义全局变量报错）

内容的提问来源于stack exchange，提问作者Sam