Kivy - 用户界面问题

Question

尝试创建一个带有两个屏幕的简单 Kivy GUI：一个标题屏幕和一个带有多个按钮的控制屏幕。主要问题是导航 GUI 并让构建器正常运行。我只是在运行时出现黑屏。import kivykivy.require('1.10.0')from kivy.lang import Builderfrom kivy.uix.screenmanager import ScreenManager, Screen, FadeTransitionfrom kivy.app import Appfrom kivy.uix.label import Labelfrom kivy.uix.image import Imagefrom kivy.uix.floatlayout import FloatLayoutfrom kivy.uix.stacklayout import StackLayoutclass IntroScreen(Screen):    passclass ContScreen(Screen):    passclass ScreenManagement(ScreenManager):    passbackbone = Builder.load_file("main.kv")class MasterApp(App):    def build (self):        return backboneboApp = MasterApp()if __name__ == "__main__":    boApp.run()与主要.kvScreenManagement:    transition: FadeTransition<IntroScreen>:    name: "main"    intro.kv<ContScreen>:    name: "cont"    stacklayout.kv和示例屏幕（intro.kv）<IntroScreen>:    FloatLayout        orientation: 'vertical'        padding: [10,50,10,50]        spacing: 50        Label:            text: 'WELCOME'            font_size: 50            pos_hint={'x':0, 'y':0}        Image:            source=('mylogo.png')            pos_hint: {'x':0,'y':0}        Button:            text: 'Initialize'            font_size: 35            on_release: app.root.current = "cont"仍在学习 Kivy，所以我知道我做错了什么。将不胜感激帮助解决这个问题。编辑：导航解决跟进：<IntroScreen>:    FloatLayout        orientation: 'vertical'        padding: [10,50,10,50]        spacing: 50        Label:            text: 'WELCOME'            font_size: 50            pos_hint: {'x':0, 'y':0}        Image:            source: 'mylogo.png'            pos_hint: {'x':0,'y':0}        Button:            text: 'Initialize'            font_size: 35            on_release: root.manager.current = "cont"图像根本不显示在屏幕上，只是完整的按钮。