```py from kivy.app import App from kivy.core.window import Window from kivy.uix.scrollview import ScrollView from kivy.uix.label import Label class MyScrollView(ScrollView): def __init__(self, **kwargs): super().__init__(**kwargs) self.size_hint = (None, None) # disable size_hint to allow fixed size self.bind(size=self.set_size) # bind the size to the window size self.set_size(Window, Window.size) def set_size(self, instance, size): self.height = size[1] * 0.8 # set the height to 80% of the window's height self.width = size[0] * 0.8 # set the width to 80% of the window's width class MyApp(App): def build(self): return MyScrollView( size_hint=(None, None), pos_hint={'center_x': 0.5, 'center_y': 0.5}, do_scroll_x=False, Label(text='This is a scrollable view'), ) if __name__ == '__main__': MyApp().run() ```