Python Kivy filechooser将多个文件添加到列表

Question

我对Python和Kivy还是比较陌生，这让我很难解决这个问题。该文件选择器正在运行，也可以选择多个文件，但它只会将最后选择的文件添加到列表中，而不会添加其余文件。我在做什么错了？

Py文件

class UploadWindow(Screen):
    paths = StringProperty()
    text_input = StringProperty()

    def show_load_list(self):
        content = LoadDialog(load=self.load_list, cancel=self.dismiss_popup)
        self._popup = Popup(title="Load the sound files", content=content, size_hint=(.5, .5))
        self._popup.open()

    def load_list(self, path, filename):
        with open(os.path.join(path, filename[0]), encoding="utf8", errors='ignore') as stream:
            filename_actual = os.path.basename(filename.pop())
            global importedfiles
            importedfiles.append((filename_actual, path))
            print(importedfiles)

        self.dismiss_popup()

    def dismiss_popup(self):
        self._popup.dismiss()

class LoadDialog(FloatLayout):
    load = ObjectProperty(None)
    cancel = ObjectProperty(None)

Kv文件

<LoadDialog>:
    BoxLayout:
        size: root.size
        pos: root.pos
        orientation: "vertical"
        FileChooserIconView:
            id: filechooser
            path: './'
            filters: ['*.wav']
            multiselect: True
        BoxLayout:
            size_hint_y: None
            height: 30
            Button:
                text: "Cancel"
                on_release: root.cancel()
            Button:
                text: "Load"
                on_release:
                    root.load(filechooser.path, filechooser.selection)