我使用的是：MacOS Big Sur，KivyMd版本-v0.104.2.dev（我试过使用稳定版本，但它仍然不能解决问题）和Python版本3.9.4。
除MDIconButton外，与KivyMD按钮（MDFlatButton、MDFilledRoundFlatIconButton、MDRaisedButton等）相关的任何内容都不起作用。
当我运行任何带有KivyMD按钮的代码时，它会给我这个错误（甚至当我尝试单击厨房Flume中的按钮选项时，窗口关闭并在终端中给我以下错误）：

[INFO   ] [Logger      ] Record log in /Users/chaithanya/.kivy/logs/kivy_21-05-10_11.txt
[INFO   ] [Kivy        ] v2.1.0.dev0
[INFO   ] [Kivy        ] Installed at "/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/kivy/__init__.py"
[INFO   ] [Python      ] v3.9.4 (v3.9.4:1f2e3088f3, Apr  4 2021, 12:32:44) 
[Clang 6.0 (clang-600.0.57)]
[INFO   ] [Python      ] Interpreter at "/Library/Frameworks/Python.framework/Versions/3.9/bin/python3"
[INFO   ] [Logger      ] Purge log fired. Processing...
[INFO   ] [Logger      ] Purge finished!
[INFO   ] [Factory     ] 189 symbols loaded
[INFO   ] [Image       ] Providers: img_tex, img_imageio, img_dds, img_sdl2, img_pil (img_ffpyplayer ignored)
[INFO   ] [Window      ] Provider: sdl2
[INFO   ] [GL          ] Using the "OpenGL ES 2" graphics system
[INFO   ] [GL          ] Backend used <sdl2>
[INFO   ] [GL          ] OpenGL version <b'2.1 INTEL-16.1.12'>
[INFO   ] [GL          ] OpenGL vendor <b'Intel Inc.'>
[INFO   ] [GL          ] OpenGL renderer <b'Intel Iris OpenGL Engine'>
[INFO   ] [GL          ] OpenGL parsed version: 2, 1
[INFO   ] [GL          ] Shading version <b'1.20'>
[INFO   ] [GL          ] Texture max size <16384>
[INFO   ] [GL          ] Texture max units <16>
[INFO   ] [Window      ] auto add sdl2 input provider
[INFO   ] [Window      ] virtual keyboard not allowed, single mode, not docked
[INFO   ] [Loader      ] using a thread pool of 2 workers
[INFO   ] [KivyMD      ] 0.104.2.dev0, git-8f83652, 2021-05-10 (installed at "/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/kivymd/__init__.py")
[INFO   ] [Text        ] Provider: sdl2
[INFO   ] [GL          ] NPOT texture support is available
[INFO   ] [Clipboard   ] Provider: sdl2(['clipboard_nspaste'] ignored)
[INFO   ] [Base        ] Start application main loop
[INFO   ] [Base        ] Leaving application in progress...
 Traceback (most recent call last):
   File "/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/kivy/lang/builder.py", line 702, in _apply_rule
     setattr(widget_set, key, value)
   File "kivy/weakproxy.pyx", line 35, in kivy.weakproxy.WeakProxy.__setattr__
   File "kivy/properties.pyx", line 520, in kivy.properties.Property.__set__
   File "kivy/properties.pyx", line 555, in kivy.properties.Property.set
   File "kivy/properties.pyx", line 1264, in kivy.properties.BoundedNumericProperty.check
 TypeError: Cannot convert kivy.properties.NumericPropertyStorage to kivy.properties.BoundedNumericPropertyStorage
 
 During handling of the above exception, another exception occurred:
 
 Traceback (most recent call last):
   File "/Users/chaithanya/KivyMD/demos/kitchen_sink/main.py", line 144, in <module>
     KitchenSinkApp().run()
   File "/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/kivy/app.py", line 955, in run
     runTouchApp()
   File "/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/kivy/base.py", line 580, in runTouchApp
     EventLoop.mainloop()
   File "/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/kivy/base.py", line 345, in mainloop
     self.idle()
   File "/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/kivy/base.py", line 389, in idle
     self.dispatch_input()
   File "/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/kivy/base.py", line 340, in dispatch_input
     post_dispatch_input(*pop(0))
   File "/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/kivy/base.py", line 306, in post_dispatch_input
     wid.dispatch('on_touch_up', me)
   File "kivy/_event.pyx", line 719, in kivy._event.EventDispatcher.dispatch
   File "/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/kivymd/uix/list.py", line 854, in on_touch_up
     super().on_touch_up(touch)
   File "/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/kivymd/uix/behaviors/ripple_behavior.py", line 296, in on_touch_up
     return super().on_touch_up(touch)
   File "/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/kivy/uix/behaviors/button.py", line 179, in on_touch_up
     self.dispatch('on_release')
   File "kivy/_event.pyx", line 719, in kivy._event.EventDispatcher.dispatch
   File "/Users/chaithanya/KivyMD/demos/kitchen_sink/main.py", line 86, in <lambda>
     "on_release": lambda x=name_item_example: self.set_example_screen(
   File "/Users/chaithanya/KivyMD/demos/kitchen_sink/main.py", line 108, in set_example_screen
     screen_object = eval(self.data_screens[name_screen]["Factory"])
   File "<string>", line 1, in <module>
   File "/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/kivy/uix/relativelayout.py", line 274, in __init__
     super(RelativeLayout, self).__init__(**kw)
   File "/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/kivy/uix/floatlayout.py", line 65, in __init__
     super(FloatLayout, self).__init__(**kwargs)
   File "/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/kivy/uix/layout.py", line 76, in __init__
     super(Layout, self).__init__(**kwargs)
   File "/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/kivymd/uix/behaviors/backgroundcolor_behavior.py", line 189, in __init__
     super().__init__(**kwargs)
   File "/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/kivymd/uix/behaviors/backgroundcolor_behavior.py", line 147, in __init__
     super().__init__(**kwarg)
   File "/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/kivymd/uix/behaviors/elevation.py", line 847, in __init__
     super().__init__(**kwargs)
   File "/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/kivy/uix/widget.py", line 359, in __init__
     self.apply_class_lang_rules(
   File "/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/kivy/uix/widget.py", line 463, in apply_class_lang_rules
     Builder.apply(
   File "/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/kivy/lang/builder.py", line 542, in apply
     self._apply_rule(
   File "/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/kivy/lang/builder.py", line 664, in _apply_rule
     self._apply_rule(
   File "/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/kivy/lang/builder.py", line 664, in _apply_rule
     self._apply_rule(
   File "/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/kivy/lang/builder.py", line 664, in _apply_rule
     self._apply_rule(
   [Previous line repeated 1 more time]
   File "/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/kivy/lang/builder.py", line 662, in _apply_rule
     child.apply_class_lang_rules(
   File "/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/kivy/uix/widget.py", line 463, in apply_class_lang_rules
     Builder.apply(
   File "/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/kivy/lang/builder.py", line 542, in apply
     self._apply_rule(
   File "/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/kivy/lang/builder.py", line 711, in _apply_rule
     raise BuilderException(rule.ctx, rule.line,
 kivy.lang.builder.BuilderException: Parser: File "<inline>", line 16:
 ...
      14:    size_hint: None, None
      15:    height: dp(20) + lbl_txt.texture_size[1]
 >>   16:    width: lbl_txt.texture_size[0] + dp(24)
      17:
      18:    MDLabel:
 ...
 TypeError: Cannot convert kivy.properties.NumericPropertyStorage to kivy.properties.BoundedNumericPropertyStorage
   File "/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/kivy/lang/builder.py", line 702, in _apply_rule
     setattr(widget_set, key, value)
   File "kivy/weakproxy.pyx", line 35, in kivy.weakproxy.WeakProxy.__setattr__
   File "kivy/properties.pyx", line 520, in kivy.properties.Property.__set__
   File "kivy/properties.pyx", line 555, in kivy.properties.Property.set
   File "kivy/properties.pyx", line 1264, in kivy.properties.BoundedNumericProperty.check

下面是我正在运行的代码，在我添加按钮之前，一切都很好：

from kivymd.app import MDApp
from kivy.lang import Builder
from kivy.uix.screenmanager import ScreenManager,Screen
##from kivy.core.window import Window
##Window.size = (280, 500)

login = '''
FloatLayout:
    MDLabel:
        pos_hint:{'center_x':.9,'center_y':.85}
        text:'LOGIN'
        font_size:80
    MDTextField:
        id:user
        hint_text:'Username'
        pos_hint:{'center_x':.5,'center_y':.75}
        size_hint:.5,.1
    MDTextField:
        id:passw
        hint_text:'Password'
        password:True
        pos_hint:{'center_x':.5,'center_y':.65}
        size_hint:.5,.1
    MDRoundFlatButton:
        text:'Login'
        pos_hint:{'center_x':.5,'center_y':.55}
        size_hint:.2,.1
    
'''

class LoginApp(MDApp):
    def build(self):
        return Builder.load_string(login)
            
if __name__ == '__main__':
    LoginApp().run()