my.kv

<WeatherDashboard>:
    ScreenManager:
        id: _screen_manager
        Screen:
            name: 'screen1' 
            BoxLayout:
                spacing: 4
                orientation: 'vertical'
                canvas:
                    Rectangle:
                        pos: self.pos
                        size: self.size
                        source: root.bg_pic 
                BoxLayout:
                    size_hint: (1, 0.2)
                    Label:
                        size_hint: (0.9, 1)
                        font_size: 48
                        text: "Weather App"
                    Button:
                        size_hint: (0.1, 1)
                        text: "setting"
                        background_normal: 'icons/setting-148.png'
                        on_press: _screen_manager.current = 'screen2'
                BoxLayout:
                    size_hint: (1, 0.8)
                    orientation: 'vertical'
                    canvas:

                        Color:
                            rgba: (0, 0, 0, 0.6)
                        Rectangle:
                            pos: (self.center_x - self.width * 0.4, self.center_y * 0.4)
                            size: (self.width * 0.8, self.height * 0.8)
                    Image:
                        source: "icons/cloudy-256.png"
                    BoxLayout:
                        Label:
                            text: root.location
                            font_size: 32
                        Label:
                            font_size: 24
                            text: 'Temperature: ' + str(root.degree) 
                        Label:
                            font_size: 24
                            text: 'Humidity: ' + str(root.humid) + '%'
        Screen:
            name: 'screen2'
            BoxLayout:
                spacing: 4
                orientation: 'vertical'
                canvas:
                    Rectangle:
                        pos: self.pos
                        size: self.size
                        source: 'wether-photos/sunny.jpg'
                BoxLayout:
                    size_hint: (1, 0.2) 
                    #TODO change to image
                    # Image:
                        # source: 'icons/back.png'
                    Button: # temp
                        text: "Back"
                        background_normal: "icons/back.png"
                        size_hint: (0.1, 1)
                        on_press: _screen_manager.current = 'screen1'
                    Label: 
                        size_hint: (0.9, 1)
                        font_size: 48
                        text: "Location"
                GridLayout:
                    size_hint: (1, 0.8)
                    cols: 3
                    padding: [100] * 4
                    ToggleButton:
                        text: "Taipei"
                        group: 'area'
                        on_press: root.change_location('Taipei')
                    ToggleButton:
                        group: 'area'
                        text: "Taoyuan"
                        on_press: root.change_location('Taoyuan')
                    ToggleButton:
                        group: 'area'
                        text: "Keelung"
                        on_press: root.change_location('Keelung')
                    ToggleButton:
                        group: 'area'
                        text: "Hsinchu"
                        on_press: root.change_location('Hsinchu')