main.kv

<MainScreen>:
    id: main_screen
    name: 'main_screen'
    BoxLayout:
        orientation: 'vertical'
        size_hint_y: None
        pos_hint: {'top': 0.9}
        MDLabel:
            text: 'DataShare'
            font_style: 'H3'
            halign: 'center'
        BoxLayout:
            orientation: 'horizontal'
            spacing: dp(20)
            padding: [dp(10), 0, dp(10), 0]
            size_hint_y: None
            MDRectangleFlatButton:
                text: "SEND"
                size_hint_x: 0.4
                text_color: app.theme_cls.opposite_bg_dark
                md_bg_color: app.theme_cls.primary_light
                on_release: app.sm.current = 'send_screen'
            MDRectangleFlatButton:
                text: "RECEIVE"
                size_hint_x: 0.4
                text_color: app.theme_cls.opposite_bg_dark
                md_bg_color: app.theme_cls.primary_dark
                on_release: app.sm.current = 'receive_screen'