Kivy：从另一个弹出窗口中关闭一个弹出窗口

Question

我kivy.factory.Factory用来打开弹出窗口，但是当我想关闭它们时它不起作用。代码：from kivy.app import Appfrom kivy.lang import Builderx = Builder.load_string("""#:import F kivy.factory.Factory#:import Window kivy.core.window.WindowScreen:    Button:        text: 'Press to Open First Popup'        on_press:            F.FirstPopup().open()<FirstPopup@Popup>:    title: 'First Popup'    size_hint: None, None    width: Window.width / 1.4    height: Window.width / 1.4    Button:        text: 'Press to Open Second Popup'        on_press: F.SecondPopup().open()<SecondPopup@Popup>:    title: 'Second Popup'    size_hint: None, None    width: Window.width / 1.8    height: Window.width / 1.8    Button:        text: 'Press to Close Both Popups'        on_press:            root.dismiss()            F.FirstPopup().dismiss() # < DOSEN'T WORK""")class MyApp(App):    def build(self):        return xMyApp().run()