如何在kivymd中定位输入的图像文件

from kivymd.app import MDApp
from kivy.uix.floatlayout import FloatLayout
from kivy.uix.image import Image
from kivymd.uix.button import MDFillRoundFlatButton

class MyApp(MDApp):
    def build(self):
        # 创建主要布局
        layout = FloatLayout()

        # 创建图像控件
        self.image = Image(source='', pos_hint={'center_x': 0.5, 'center_y': 0.7}, size_hint=(0.5, 0.5))
        layout.add_widget(self.image)

        # 创建按钮控件
        button = MDFillRoundFlatButton(text="选择图像文件", pos_hint={'center_x': 0.5, 'center_y': 0.3},
                                       on_release=self.open_file_dialog)
        layout.add_widget(button)

        return layout

    def open_file_dialog(self, obj):
        # 打开文件对话框
        from tkinter import Tk, filedialog
        Tk().withdraw()
        filename = filedialog.askopenfilename()

        # 更新图像控件的源图像
        self.image.source = filename

    def on_start(self):
        # 显示图像
        self.open_file_dialog(None)

if __name__ == '__main__':
    MyApp().run()