test.py

# testing environment for gui

import os

from kivy.core.window import Window
from kivy.lang import Builder

from kivymd.app import MDApp
from kivymd.uix.filemanager import MDFileManager
from kivymd.toast import toast


KV = '''
MDBoxLayout:
    orientation: "vertical"

    MDTopAppBar:
        title: "Image Converter"
        elevation: 3

    MDFloatLayout:

        MDRoundFlatIconButton:
            text: "Open manager"
            icon: "folder"
            pos_hint: {"center_x": .5, "center_y": .5}
            on_release: app.file_manager_open()
'''


class Example(MDApp):
    def __init__(self, **kwargs):
        super().__init__(**kwargs)
        Window.bind(on_keyboard=self.events)
        self.manager_open = False
        self.file_manager = MDFileManager(
            exit_manager=self.exit_manager, select_path=self.select_path, preview=True
        )

    def build(self):
        self.theme_cls.theme_style = "Dark"
        self.theme_cls.primary_palette = "Orange"
        return Builder.load_string(KV)

    def file_manager_open(self):
        self.file_manager.show(os.path.expanduser("~"))  # output manager to the screen
        self.manager_open = True

    def select_path(self, img_path: str):
        '''
        It will be called when you click on the file name
        or the catalog selection button.

        :param path: path to the selected directory or file;
        '''

        self.exit_manager()
        print(img_path)
        toast(img_path)

    def exit_manager(self, *args):
        '''Called when the user reaches the root of the directory tree.'''

        self.manager_open = False
        self.file_manager.close()

    def events(self, instance, keyboard, keycode, text, modifiers):
        '''Called when buttons are pressed on the mobile device.'''

        if keyboard in (1001, 27):
            if self.manager_open:
                self.file_manager.back()
        return True


Example().run()