Kivy ScreenManager 打破 BoxLayout

Question

我是 Kivy 的新手，但能够创建一个单屏应用程序。在我需要添加更多屏幕之前，一切看起来都不错。一页应用程序显示正确，但是当我添加屏幕时，BoxLayouts 不再按我预期的那样工作。所有小部件都在屏幕底部相互叠加。我的问题是我在实施 ScreenManager 时做错了什么？单屏应用程序如下所示：我决定将其设为多屏，但是当我添加 ScreenManager 逻辑时，生成的屏幕如下所示：我的 main.py 文件如下所示：from kivy.app import Appfrom kivy.uix.boxlayout import BoxLayoutfrom kivy.uix.label import Labelfrom kivy.uix.button import Buttonfrom kivy.uix.popup import Popupfrom kivy.properties import ObjectPropertyfrom kivy.uix.screenmanager import ScreenManager, Screen, FadeTransitionclass Pay_screen(Screen):    passclass Survey_screen(Screen):    passclass Finish_screen(Screen):    passclass Sm(ScreenManager):    passclass Next_root(BoxLayout):    passclass Nq_disagree_label(Label):    passclass Nq_question_label(Label):    passclass Nq_button(Button):    passclass survey_form(BoxLayout):    #dept_button = ObjectProperty()    def send_survey(self):        mypopup = MyPopup()        mypopup.show_popup('Survey', 'Survey sent!', 'OK!')    def add_comment(self):        mypopup = MyPopup()        mypopup.show_popup('Comment', 'This is where a comment is added.', 'OK!')    def close_app(self):        App.get_running_app().stop()class MyPopup(Popup):    def show_popup(self, title_text, label_text, button_text):        mytext= label_text        content = BoxLayout(orientation="vertical")        content.add_widget(Label(text=mytext, font_size=20, text_size=(300, None)))        mybutton = Button(text="Ok!", size_hint=(1,.20), font_size=20)        content.add_widget(mybutton)        mypopup = Popup(content = content,                                      title = title_text,                             auto_dismiss = False,                                 size_hint = (.5, .5)) #,                                 #font_size = 20)        mybutton.bind(on_press=mypopup.dismiss)          mypopup.open()  class nextqualApp(App):    icon = 'nextqual.png'    title = 'Pay / survey / join'if __name__ == '__main__':    nextqualApp().run()