screenselectpath.kv

<ScreenSelectPath>:
    name: "ScreenSelectPath"

    MDBoxLayout: 
        orientation: "vertical"
        spaceing:20
        MDBoxLayout:
            size_hint_y:.30
            orientation: "vertical"
            MDRelativeLayout:
                size_hint_y:.30
                MDLabel:
                    pos_hint:{"center_x": .50, "center_y": .50}
                    text:"当前目录:"
                MDRectangleFlatIconButton:
                    pos_hint:{"center_x": .35, "center_y": .5}
                    id: id_btn_back
                    text: "up"
                    icon: "keyboard-return"
                    theme_text_color: "Custom"
                    theme_icon_color: "Custom"
                    icon_color: "orange"
                    on_release: app.toUperLevelDir()
            MDBoxLayout:
                size_hint_y:.70
                MDTextField:
                    id:id_cur_path
                    size_hint_y:.7
                    max_text_length:255
                    multiline:True
                    mode: "line"
        MDBoxLayout: 
            size_hint_y:.60
            orientation: "vertical"
            MDLabel:
                size_hint_y:.05
                text: "子目录"        
            MDScrollView:
                size_hint_y:.95
                MDList:
                    id: id_dir_list
        MDBoxLayout:
            size_hint_y:.10
            orientation: "horizontal"
            MDRelativeLayout:
                MDRectangleFlatButton:
                    id:id_btn_ok
                    pos_hint:{"center_x": .25, "center_y": .5}
                    text: "确定"
                    theme_text_color: "Custom"
                    text_color: "orange"
                    #on_release:动态绑定
                MDRectangleFlatButton:
                    pos_hint:{"center_x": .75, "center_y": .5}
                    text: "取消"
                    on_release:app.back_mainScreen()