Develop Reference

How can I change default active item of Bottom Navigation in kivymd?

I am a beginner in kivymd. I was trying to create bottom-navigation in kivymd. After run the code the it showing active item of Bottom Navigation is 'Home'(name='screen_1). Now I want second item as default active item -> 'Features'(name='screen_2'). This is sample code.
from kivymd.app import MDApp
from kivy.lang import Builder
from kivy.core.window import Window
Window.size=(350,593)
KV_string = """
Screen:
BoxLayout:
orientation:'vertical'
MDToolbar:
title:'Demo Application'
right_action_items : [["dots-vertical"]]
left_action_items : [["menu", lambda x: app.menu_toggle()]]
right_action_items : [["dots-vertical", lambda x: app.option_fun()]]
elevation:10
MDLabel:
text:'Welcome to good GUI'
halign:'center'
MDBottomNavigation:
MDBottomNavigationItem:
name: 'screen_1'
text: 'Home'
icon: 'home-outline'
on_tab_press: app.Bottom_nav_fun()
MDLabel:
text: 'Home page'
halign: 'center'
MDBottomNavigationItem:
name: 'screen_2'
text: 'Features'
icon: 'feature-search-outline'
MDLabel:
text: 'Features of this app'
halign: 'center'
MDBottomNavigationItem:
name: 'screen_3'
text: 'Developers'
icon: 'account-supervisor'
MDLabel:
text: 'Developers details'
halign: 'center'
"""
class MyApp(MDApp):
def build(self):
self.theme_cls.primary_palette="Blue"
self.theme_cls.theme_style="Light"
self.theme_cls.primary_hue="A700"
self.screen = Builder.load_string(KV_string)
return self.screen
def menu_toggle(self):
print("Menu toggle Working")
def option_fun(self):
print("Option method Working")
def Bottom_nav_fun(self):
print("Bottom nav home")
if __name__=='__main__':
MyApp().run()
Is there any way to implement this?

Use method switch_tab which takes as argument the name of the tab you want to switch to - https://kivymd.readthedocs.io/en/latest/components/bottomnavigation/#how-to-automatically-switch-a-tab

(KivyMD) How to call a function when using 2 kv files/strings?

I have a kivymd app that has a screen with a button on it. When you click this button an MDCard will appear on the screen. When you click on this new MDCard it will call a function that will print a message on the terminal. However, I am having trouble getting this MDCard to call the function. I am getting the error:
AttributeError: 'MDCard' object has no attribute 'option'
The MDCard is in a separate kv string from the main kv string. Essentially I have two kv strings. When you press the button, the second kv string will be added as a widget to the first kv string.
I figured it is because the second kv string doesn't have a class as a root but I don't know how to do this. How can I get the MDCard to call the function??
MAIN.PY
from kivy.lang import Builder
from kivy.uix.boxlayout import BoxLayout
from kivy.properties import ObjectProperty
from kivymd.app import MDApp
from button_screen import button_screen
MainNav = '''
<ContentNavigationDrawer>:
ScrollView:
MDList:
OneLineListItem:
text: 'Go to Button Screen'
on_press:
root.nav_drawer.set_state("close")
root.screen_manager.current = "go_to_button_screen"
Screen:
MDToolbar:
id: toolbar
pos_hint: {"top": 1}
elevation: 10
left_action_items: [["menu", lambda x: nav_drawer.set_state("open")]]
MDNavigationLayout:
x: toolbar.height
ScreenManager:
id: screen_manager
Screen:
name: "words_nav_item"
button_screen:
name: "go_to_button_screen"
MDNavigationDrawer:
id: nav_drawer
ContentNavigationDrawer:
screen_manager: screen_manager
nav_drawer: nav_drawer
'''
class ContentNavigationDrawer(BoxLayout):
screen_manager = ObjectProperty()
nav_drawer = ObjectProperty()
class main_test(MDApp):
def build(self):
self.theme_cls.primary_palette = "Red"
return Builder.load_string(MainNav)
main_test().run()
BUTTON SCREEN .PY FILE
from kivy.lang import Builder
from kivymd.uix.screen import MDScreen
button_screen_kv = '''
<button_screen>:
MDGridLayout:
cols: 1
size: root.width, root.height
spacing: 40
md_bg_color: [0,0,.1,.1]
MDGridLayout:
cols: 1
size_hint_y: None
height: 40
MDGridLayout:
cols: 1
Button:
text: "Click to add card"
on_release:
root.add_card("card 1")
MDGridLayout:
id: add_card_here_id
cols: 1
'''
md_card_kv = '''
MDCard:
orientation: 'vertical'
size_hint: None, None
size: "360dp", "120dp"
ripple_behavior: True
on_release:
root.option("MDCard was clicked")
MDLabel:
id: LabelTextID
text: "this is an MDCard"
halign: 'center'
'''
class button_screen(MDScreen):
def __init__(self, **kwargs):
super().__init__(**kwargs)
Builder.load_string(button_screen_kv)
self.md_card_widget = Builder.load_string(md_card_kv)
def option(self, string):
print(f"{string}")
def add_card(self, *args):
self.ids.add_card_here_id.add_widget(self.md_card_widget)

I came up with the following that works however, I am still new to programming so I don't know if this is a stable solution. Please advise me there
The Solution:
I added another class class user_card(MDGridLayout) in the buttonscreen.py and placed the kv string there.
I set that class as the root widget in the kv string
in the init method I placed a function that will return the kv string return self.user_card_string
then I added that class as a parameter in the add_widget and passed the col as an argument: self.ids.add_card_here_id.add_widget(user_card(cols=1))
Everything works but I have never used two classes before. So I am unsure if this will present a future problem.
button_screen.py:
from kivy.lang import Builder
from kivymd.uix.gridlayout import MDGridLayout
from kivymd.uix.screen import MDScreen
button_screen_kv = '''
<button_screen>:
MDGridLayout:
cols: 1
size: root.width, root.height
spacing: 40
md_bg_color: [0,0,.1,.1]
MDGridLayout:
cols: 1
size_hint_y: None
height: 40
MDGridLayout:
cols: 1
Button:
text: "Click to add card"
on_release:
root.add_card("card 1")
MDGridLayout:
id: add_card_here_id
cols: 1
'''
md_card_kv = '''
<user_card>:
MDGridLayout:
cols: 1
MDCard:
orientation: 'vertical'
size_hint: None, None
size: "360dp", "120dp"
ripple_behavior: True
on_release:
root.option()
MDLabel:
id: LabelTextID
text: "this is an MDCard"
halign: 'center'
'''
class user_card(MDGridLayout):
user_card_string = Builder.load_string(md_card_kv)
def __init__(self, *args, **kwargs):
super().__init__(**kwargs)
self.load_card()
def option(self, *args):
print("MDCard was clicked")
def load_card(self):
return self.user_card_string
class button_screen(MDScreen):
def __init__(self, **kwargs):
super().__init__(**kwargs)
Builder.load_string(button_screen_kv)
def add_card(self, *args):
self.ids.add_card_here_id.add_widget(user_card(cols=1))

How do I pass an argument between KivyMD screens?

When going from the first screen to the second screen, I want to pass a variable as an argument so that kivyMD can update the second screen from text stored in an excel file. The following is a skeleton of my app's functionality:
The user reaches Screen 1 thru the navigation drawer in KivyMD, screen 1 presents the user with two options on two small clickable MDCards:
"Change text to 1"
"Change text to 2"
After clicking on one of these, the app switches to screen 2 with a single big MDCard, the text on this MDCard should change to reflect the option the user chose.
However, kivy is pulling the text that is to be displayed on the big MDCard from an excel file.
The variable that I want to pass from screen 1 to screen 2 is simply a number (1 or 2) that will tell kivy which row in the excel file it should pull the text from
If the user clicks "Change text to 1" then the first screen should pass "1" as the argument row_x to the function def change_text() (see screen 2 .py) so that the text in row 1 of excel can be displayed on the second screen. How can I achieve this?
I have 4 files in total; 3 are .py files (one for the main app, one for screen 1, and one for screen 2), and the excel file
NOTE: in the code below, Screen 1 & 2 are called Element 1 & 2 respectfully
Main.py:
from kivy.lang import Builder
from kivy.uix.boxlayout import BoxLayout
from kivy.properties import ObjectProperty
from kivymd.app import MDApp
from element_1 import element_1_screen
from element_2 import element_2_screen
MainNavigation = '''
<ContentNavigationDrawer>:
ScrollView:
MDList:
OneLineListItem:
text: 'Go to Element 1'
on_press:
root.nav_drawer.set_state("close")
root.screen_manager.current = "go_to_element_1_screen"
Screen:
MDToolbar:
id: toolbar
pos_hint: {"top": 1}
elevation: 10
left_action_items: [["menu", lambda x: nav_drawer.set_state("open")]]
MDNavigationLayout:
x: toolbar.height
ScreenManager:
id: screen_manager
Screen:
name: "words_nav_item"
element_1_screen:
name: "go_to_element_1_screen"
element_2_screen:
name: "go_to_element_2_screen"
MDNavigationDrawer:
id: nav_drawer
ContentNavigationDrawer:
screen_manager: screen_manager
nav_drawer: nav_drawer
'''
class ContentNavigationDrawer(BoxLayout):
screen_manager = ObjectProperty()
nav_drawer = ObjectProperty()
class mainApp(MDApp):
def build(self):
self.theme_cls.primary_palette = "Red"
return Builder.load_string(MainNavigation)
mainApp().run()
Screen 1 / Element 1
from kivy.lang import Builder
from kivymd.uix.screen import MDScreen
element_1_contents = '''
<element_1_screen>:
MDGridLayout:
rows: 2
size: root.width, root.height
pos_hint: {"center_x": .8, "center_y": .2}
spacing: 40
MDCard:
orientation: 'vertical'
size_hint: None, None
size: "360dp", "120dp"
ripple_behavior: True
on_release:
root.manager.current = "go_to_element_2_screen"
MDLabel:
id: LabelTextID
text: "Change Text to 1"
halign: 'center'
MDCard:
orientation: 'vertical'
size_hint: None, None
size: "360dp", "120dp"
ripple_behavior: True
on_release:
root.manager.current = "go_to_element_2_screen"
MDLabel:
id: LabelTextID
text: "Change Text to 2"
halign: 'center'
'''
class element_1_screen(MDScreen):
def __init__(self, **kwargs):
super().__init__(**kwargs)
Builder.load_string(element_1_contents)
Screen 2 / Element 2
from kivy.lang import Builder
from kivymd.uix.screen import MDScreen
import openpyxl
element_2_contents = '''
<element_2_screen>:
MDCard:
orientation: 'vertical'
size_hint: None, None
size: "360dp", "360dp"
pos_hint: {"center_x": .5, "center_y": .5}
ripple_behavior: True
focus_behavior: True
on_release: root.manager.current = "go_to_element_1_screen"
MDLabel:
id: TextID
text: "NOTHING HAS CHANGED"
halign: 'center'
MDLabel:
text: "(Click here to return)"
halign: 'center'
'''
class element_2_screen(MDScreen):
def __init__(self, **kwargs):
super().__init__(**kwargs)
path = "data.xlsx"
self.wb_obj = openpyxl.load_workbook(path)
self.sheet_obj = self.wb_obj.active
Builder.load_string(element_2_contents)
def change_text(self, row_x=0):
row_number = self.sheet_obj.cell(row_x, column=1)
self.ids.TextID.text = str(row_number.value)
And the excel file only has two entries in Column A:
Row 1: You have chosen 1
Row 2: You have chosen 2

I found the answer and now it works flawlessly. Someone over on Reddit (u/Username_RANDINT) helped me, this is what they said:
The ScreenManager has a get_screen() method. You could use it to get
the instance of the second screen and call the change_text() method on
that. In the same place where you switch screens, add another line:
on_release:
root.manager.current = "go_to_element_2_screen"
root.manager.get_screen("go_to_element_2_screen").change_text(1)
Then the same for the other card, just pass in 2 instead of 1.

KivyMD MDNavigationRail, press icons

I was trying to use a new feature in KivyMD, the MDNavigationRail and wanted to give the icons in it a function. The goal is that the user could change to the desired screen by pressing the icon that represents it. I gave the icon an on_press. But something goes wrong, I get an error; ValueError: MDNavigationRail.state is set to an invalid option 'down'. Must be one of: ['close', 'open']. The rail should be open or closed I guess, isn't it possible to give it a function? Furthermore, I would want to know if it is possible to not break the text. If anyone could help me out, it would be very nice!
My .py file
from kivy.uix.screenmanager import ScreenManager
from kivymd.app import MDApp
from kivymd.uix.screen import MDScreen
class Screen1(MDScreen):
def screen2(self):
self.manager.current = 'screen2'
class Screen2(MDScreen):
def screen1(self):
self.manager.current = 'screen1'
def rail_open(self):
if self.ids.rail.state == "open":
self.ids.rail.state = "close"
else:
self.ids.rail.state = "open"
class MyScreenManager(ScreenManager):
def __init__(self, **kwargs):
super(MyScreenManager, self).__init__(**kwargs)
class Test(MDApp):
def build(self):
return MyScreenManager()
Test().run()
My kv file
<MyScreenManager>:
Screen1:
id: screen1
name: 'screen1'
Screen2:
id: screen2
name: 'screen2'
<Screen1>:
id: screen1
MDFloatLayout:
MDRectangleFlatButton:
text: "Change to screen 2"
on_press: root.screen2()
pos_hint: {'center_x':0.5, 'center_y':0.5}
<Screen2>:
id: screen2
MDBoxLayout:
orientation: "vertical"
MDToolbar:
left_action_items: [["menu", lambda x: root.rail_open()]]
MDBoxLayout:
MDNavigationRail:
id: rail
elevation: 1
use_resizeable: True
MDNavigationRailItem:
icon: "home"
text: "homepage"
on_press: root.screen1()
MDNavigationRailItem:
icon: ""
text: ""
MDFloatLayout:
MDTextField:
id: field1
hint_text: "Enter something:"
size_hint_x: 0.4
pos_hint: {'center_x':0.25,'top':0.8}

It was a bug. Already fixed - https://github.com/kivymd/KivyMD/commit/8a31b0f3ccad9c2d9ad35d80953f7396f2dc78f2

KivyMD: Contents of Screen overlap with Toolbar

I'm writing a simple app in KivyMD. According to the kivy documentation my .kv structure with MDNavigationDrawer and MDToolbar is right and everything works fine as long as the screens are empty. When I add content to them, the content instead of being under the Toolbar is above it. How can I fix it?
Here is my code:
from kivy.lang import Builder
from kivy.uix.boxlayout import BoxLayout
from kivy.properties import ObjectProperty
from kivymd.app import MDApp
KV = '''
<ContentNavigationDrawer>:
ScrollView:
MDList:
OneLineListItem:
text: "Screen 1"
on_press:
root.nav_drawer.set_state("close")
root.screen_manager.current = "scr 1"
OneLineListItem:
text: "Screen 2"
on_press:
root.nav_drawer.set_state("close")
root.screen_manager.current = "scr 2"
Screen:
MDToolbar:
id: toolbar
pos_hint: {"top": 1}
elevation: 10
title: "Test"
left_action_items: [["menu", lambda x: nav_drawer.set_state("open")]]
NavigationLayout:
x: toolbar.height
ScreenManager:
Screen:
name: "scr 1"
ScrollView:
BoxLayout:
orientation: "vertical"
Button:
text: "Hello"
Button:
text: "I wish"
Button:
text: "I could"
Button:
text: "Finally get"
Button:
text: "This to work"
Screen:
name: "scr 2"
MDLabel:
text: "Screen 2"
halign: "center"
MDNavigationDrawer:
id: nav_drawer
ContentNavigationDrawer:
screen_manager: screen_manager
nav_drawer: nav_drawer
'''
class ContentNavigationDrawer(BoxLayout):
screen_manager = ObjectProperty()
nav_drawer = ObjectProperty()
class TestNavigationDrawer(MDApp):
def build(self):
return Builder.load_string(KV)
TestNavigationDrawer().run()
Output of the following code:

The Screen class is a RelativeLayout, so you must position its children as you would any RelativeLayout. Every child of the Screen gets the default size_hint of (1,1) and the default pos of (0,0), so you must adjust it if that is not what you want. In your case, the NavigationLayout will completely cover the Screen based on those default values. You can fix that by just adding a size_hint_y, like this:
NavigationLayout:
x: toolbar.height
size_hint_y: 1.0 - toolbar.height/root.height
This sets the size of the NavigationLayout so that it just meets the bottom of the MDToolbar instead of overlpping it.

It's the order of appearance that is the problem:
If the screen has other widgets such as cards and Layouts, all of these must appear first.
i.e. put the Navigation Layout and the respective screen manager at the bottom.
What comes last appears on top of everything else.
That worked for me.

A most elegant solution is to insert the MDToolbar and NavigationLayout into a BoxLayout with orientation: "vertical" so the NavigationLayout start at the bottom of the Toolbar, without calculating the relative position.
Screen:
BoxLayout:
orientation: "vertical"
MDToolbar:
MDNavigationLayout: