Kivy 相机的最后一帧仍保留在屏幕上

我写了一个启动和停止相机的代码。

当用户单击按钮时 "Stop Camera", 视频成功停止。 问题是最后一个视频帧保留在屏幕上。

用户停止相机后如何获得清洁背景？

https://i.stack.imgur.com/rW5pH.png

from kivy.app import App

from kivy.lang import Builder

from kivy.uix.screenmanager import Screen, ScreenManager



Builder.load_string/"""

<camerascreen>:

 GridLayout:

 id: grid1

 cols: 1

 Camera:

 id: camera

 resolution: /640, 480/

 play: False

 ToggleButton:

 id: camera_button

 text: 'Start Camera'

 on_press: root.play//



<rootwidget>:

 canvas.before:

 Color:

 rgba: 1, 1, 1, 1

 Rectangle:

 pos: self.pos

 size: self.size

 CameraScreen:

 id: camera_screen

 name: "camera_screen"

"""/

class CameraScreen/Screen/:



 def play/self/:

 if self.ids.camera.play == False:

 self.ids.camera.play = True

 self.ids.camera_button.text = "Stop Camera"

 else:

 self.ids.camera.play = False

 self.ids.camera_button.text = "Start Camera"





class RootWidget/ScreenManager/:

 pass



class MainApp/App/:

 def build/self/:

 return RootWidget//





MainApp//.run//

</rootwidget></camerascreen>