Kivy摄像头不能在android手机上保存图片

<uses-permission android:name="android.permission.CAMERA" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

from jnius import autoclass

# 获取Camera类
Camera = autoclass('android.hardware.Camera')

# 打开摄像头
camera = Camera.open()

# 设置摄像头参数
params = camera.getParameters()
params.setPictureFormat(256)  # JPEG格式
camera.setParameters(params)

# 拍照
camera.takePicture(None, None, None, MyPictureCallback())

# 图片回调函数
class MyPictureCallback(autoclass('android.hardware.Camera$PictureCallback')):
    def onPictureTaken(self, data, camera):
        # 保存图片到本地
        file_path = '/sdcard/my_picture.jpg'
        with open(file_path, 'wb') as f:
            f.write(data)
        camera.release()