如何使用 kivy 在屏幕上添加文本？

Question

这是代码，我想在主屏幕上添加文本，但在互联网上没有找到解决方案。 请帮助）谢谢）

from kivy.app import App
from kivy.core.window import Window
from kivy.uix.button import Button
from kivy.uix.screenmanager import ScreenManager, Screen
from kivy.uix.floatlayout import FloatLayout
from kivy.uix.label import Label

Window.clearcolor = '#121212'
class MainApp(App):
    def build(self):
        # Add the main and second screens to the manager, this class does nothing else
        sm.add_widget(MainScreen())
        sm.add_widget(SecondScreen())
        sm.add_widget(ThirdScreen())
        return sm  # Return the manager to work with him later

class MainScreen(Screen):
    def __init__(self):
        super().__init__()
        self.name = 'Main'  # setting the screen name value for the screen manager
        # (it's more convenient to call by name rather than by class)
        main_layout = FloatLayout()  # creating an empty layout that's not bound to the screen
        self.add_widget(main_layout)  # adding main_layout on screen

        # Button to get to the 2nd screen
        three_players = Button(text='3 players',
                            bold=True,
                            background_normal='',
                            background_color='#565656',
                            pos_hint={'center_x': .5, 'center_y': .35},
                            size_hint=(.7, .12),
                            color='#000000')
        three_players.bind(on_press=self.to_second_scrn)

        # Button to get to the 3rd screen
        four_players = Button(text='4 players',
                            bold=True,
                            background_normal='',
                            background_color='#565656',
                            pos_hint={'center_x': .5, 'center_y': .2},
                            size_hint=(.7, .12),
                            color='#000000')
        four_players.bind(on_press=self.to_third_scrn)

        main_layout.add_widget(three_players)
        main_layout.add_widget(four_players) # adding button on layout

    def to_second_scrn(self, *args):
        self.manager.current = 'Second'  # selecting the screen by name (in this case by name "Second")

    def to_third_scrn(self, *args):
        self.manager.current = 'Third'  # selecting the screen by name (in this case by name "Thrid")

    def build(self):
        title = Label(text="ABOBA",
                      pos_hint={'center_x': 1, 'center_y': .9},
                      )

        return title

class SecondScreen(Screen):
    def __init__(self):
        super().__init__()
    # on this screen, I do everything the same as on the main screen to be able to switch back and forth
        self.name = 'Second'
        second_layout = FloatLayout()
        self.add_widget(second_layout)

        Button
        Go_Back = Button(text='Go to Main screen',
                         size_hint=(.5, .5),
                         pos_hint={'center_x': .5, 'center_y': .5},
                         color='#ffff00')
        Go_Back.bind(on_press=self.to_main_scrn)

        second_layout.add_widget(Go_Back)

    def to_main_scrn(self, *args):  # together with the click of the button, it transmits info about itself.
        # In order not to pop up an error, add *args to the function
        self.manager.current = 'Main'
        return 0


class ThirdScreen(Screen):
    def __init__(self):
        super().__init__()
    # on this screen, do everything the same as on the main screen to be able to switch back and forth
        self.name = 'Third'
        third_layout = FloatLayout()
        self.add_widget(third_layout)

        # Button
        Go_Back = Button(text='Go to Main screen',
                         size_hint=(.5, .5),
                         pos_hint={'center_x': .5, 'center_y': .5},
                         color='#ffff00')

        Go_Back.bind(on_press=self.to_main_scrn)

        third_layout.add_widget(Go_Back)

    def to_main_scrn(self, *args):  # together with the click of the button, it transmits info about itself.
        # In order not to pop up an error, add *args to the function
        self.manager.current = 'Main'
        return 0


sm = ScreenManager()

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

尝试将新函数添加到返回标签的 MainApp 类中，但没有成功。 但是如果我将它添加到构建函数中，它就会起作用，但其他任何东西都不起作用。 hdddddddddddddddddddddddddd

Answer 1

要从 App 类将 Label 添加到主屏幕，您需要访问小部件树并获取已添加到屏幕的 FloatLayout，并将 Label 小部件添加到该布局。

App 方法 on_start() 在构建完成后调用。 将下面的代码添加到您的 App 类中，这会将标签添加到主屏幕。

    def on_start(self):
        # get the main screen, FloatLayout
        main_screen_layout = self.root.get_screen('Main').children[0]
        main_screen_layout.add_widget(Label(text="Title", pos_hint={'center_x': 0.5, 'center_y': .9}))

• 自己是应用程序
• self.root 是屏幕管理器
• self.root.get_screen('Main') 是 MainScreen 实例
• self.root.get_screen('Main').children[0] 是 MainScreen 实例上的 FloatLayout。