menu.py
from kivy.app import App
from kivy.uix.dropdown import DropDown
from kivy.lang import Builder
class CustDrop(DropDown):
    def __init__(self, **kwargs):
        super(CustDrop, self).__init__( **kwargs)
        self.select('')
kv_str = Builder.load_string('''
BoxLayout:
    orientation: 'vertical'
    BoxLayout:
        canvas.before:
            Rectangle:
                pos: self.pos
                size: self.size
            Color:
                rgb: (1,1,1)
        size_hint_y:1
        Button:
            id: btn
            text: 'user'
            on_release: dropdown.open(self)
            #size_hint_y: None
            #height: '48dp'  
        CustDrop:
            id: dropdown
            Button:
                text: 'List User'
                size_hint_y: None
                height: '48dp'
        Label:
            size_hint_x: 4
    Label:
        size_hint_y: 9
''')
class ExampleApp(App):
    def build(self):
        return kv_str
if __name__ =='__main__':
    ExampleApp().run()
user.py
import kivy
kivy.require('1.9.0')  # replace with your current kivy version !
import sqlite3 as lite
from kivy.app import App
from kivy.uix.boxlayout import BoxLayout
from kivy.properties import BooleanProperty, ListProperty, StringProperty, ObjectProperty,NumericProperty
from kivy.lang import Builder
from kivy.uix.recycleview.views import RecycleDataViewBehavior
from kivy.uix.button import Button
from kivy.uix.recyclegridlayout import RecycleGridLayout
from kivy.uix.behaviors import FocusBehavior
from kivy.uix.recycleview.layout import LayoutSelectionBehavior
from kivy.uix.popup import Popup
from kivy.core.window import Window
Window.size = (500, 500)
#con = lite.connect('user.db')
#con.text_factory = str
#cur = con.cursor()
class SelectableRecycleGridLayout(FocusBehavior, LayoutSelectionBehavior,
                                  RecycleGridLayout):
    ''' Adds selection and focus behaviour to the view. '''
class SelectableButton(RecycleDataViewBehavior, Button):
    ''' Add selection support to the Button '''
    index = None
    selected = BooleanProperty(False)
    selectable = BooleanProperty(True)
    def refresh_view_attrs(self, rv, index, data):
        ''' Catch and handle the view changes '''
        self.index = index
        return super(SelectableButton, self).refresh_view_attrs(rv, index, data)
    def on_touch_down(self, touch):
        ''' Add selection on touch down '''
        if super(SelectableButton, self).on_touch_down(touch):
            return True
        if self.collide_point(*touch.pos) and self.selectable:
            return self.parent.select_with_touch(self.index, touch)
    def apply_selection(self, rv, index, is_selected):
        ''' Respond to the selection of items in the view. '''
        self.selected = is_selected
    def on_press(self,*args):
        popup = TextInputPopup(self)
        popup.open()
    def update_changes(self):
        self.text = txt
class RV(BoxLayout):
    data_items = ListProperty([])
    def __init__(self, **kwargs):
        super(RV, self).__init__(**kwargs)
        self.get_users()
    def get_users(self):
        # cur.execute("SELECT * FROM `users` order by id asc")
        # rows = cur.fetchall()
        rows = [(1, 'Yash', 'Chopra'),(2, 'amit', 'Kumar')]
        for row in rows:
            for col in row:
                self.data_items.append(col)
class ListUser(App):
    title = "Users"
    def build(self):
        self.root = Builder.load_file('user.kv')
        return RV()
if __name__ == '__main__':
    ListUser().run()
user.kv
#:kivy 1.10.0
<SelectableButton>:
    # Draw a background to indicate selection
    canvas.before:
        Color:
            rgba: (.0, 0.9, .1, .3) if self.selected else (0, 0, 0, 1)
        Rectangle:
            pos: self.pos
            size: self.size
<RV>:
    BoxLayout:
        orientation: "vertical"
        GridLayout:
            size_hint: 1, None
            size_hint_y: None
            height: 25
            cols: 3
            Label:
                text: "ID"
            Label:
                text: "First Name"
            Label:
                text: "Last Name"
        BoxLayout:
            RecycleView:
                viewclass: 'SelectableButton'
                data: [{'text': str(x)} for x in root.data_items]
                SelectableRecycleGridLayout:
                    cols: 3
                    default_size: None, dp(26)
                    default_size_hint: 1, None
                    size_hint_y: None
                    height: self.minimum_height
                    orientation: 'vertical'
                    multiselect: True
                    touch_multiselect: True
I have two file menu.py and user.py. menu.py file show menu and user.py shows list of user..
when i run menu.py then shows user menu on top .When i click on user then 'list user' show(submenu of user).When i click on 'list user' then user list should show  in current window.Menu will be on top and user-list show in same window(under menu).
 
    
