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python kivy app stops functioning after adding widget (on PC)

I removed everything superfluous, leaving only what was necessary to reproduce the same behavior.
There is an MD Text Field in which, when entering text, if there are matches, MDDropdownMenu appears with options to choose from. The options are stored in the P_LIST list. If you don't enter text into this Mytextfield, everything works. As soon as you enter the text, the function is triggered, a menu appears, you select. After that, the application does not function.
I determined that this is happening because of the line: self.add_widget(list drop down) # <----------- marked in the code
The menu appears without add_widget, but if you enter more than one letter, a new instance of the ListDropdownValue class is created each time and the menus overlap.
#kivymd 0.104.2
#kivy 2.0.0
from kivy.clock import Clock
from kivy.lang import Builder
from kivy.metrics import dp
from kivy.properties import ObjectProperty
from kivymd.app import MDApp
from kivy.uix.boxlayout import BoxLayout
from kivymd.uix.menu import MDDropdownMenu
kv_str = """
<StartScreen>:
startscreen_textfield_1: textfield_id
BoxLayout:
orientation: "vertical"
BoxLayout:
size_hint: 1, 0.5
BoxLayout:
size_hint: 1, 0.5
orientation: "vertical"
BoxLayout:
MDTextField:
id: textfield_id
on_text:
root.open_listdropdown(textfield_id)#
BoxLayout:
MDTextField:
BoxLayout:
MDTextField:
"""
P_LIST = ["ASD", "SDF", "AASD"]
def search_product(prefix):
filtered_list = []
filtered_list = list(filter(lambda l: l.startswith(prefix), P_LIST))
return filtered_list
class MyListDropdownValue(MDDropdownMenu):
def __init__(self, dropdown_list, **kwargs):
super().__init__(**kwargs)
self.dropdown_list_id = dropdown_list
def list_dropdown(self):
if len(self.dropdown_list_id.text) != 0:
prefix = self.dropdown_list_id.text.upper()
filtered_list = search_product(prefix)
menu_items = [{'text':f'{value}',
"height": dp(56),
"viewclass": "OneLineListItem",
"on_release": lambda x= f"{value}": self.set_item(x)}
for value in filtered_list]
self.menu = MDDropdownMenu(
caller=self.dropdown_list_id,
items=menu_items,
width_mult=5,
)
self.menu.open()
def set_item(self, value):
def set_item(interval):
self.dropdown_list_id.text = value
self.menu.dismiss()
Clock.schedule_once(set_item, 0.1)
class StartScreen(BoxLayout):
startscreen_textfield_1 = ObjectProperty()
def open_listdropdown(self, id):
if len(self.children) == 1:
listdropdown = MyListDropdownProduct(id)
self.add_widget(listdropdown)
self.children[0].list_dropdown()
else:
self.children[0].menu.dismiss()
self.children[0].list_dropdown()
kv = Builder.load_string(kv_str)
class Program(MDApp):
def build(self):
self.screen = StartScreen()
return self.screen
def main():
app = Program()
app.run()
if __name__ == "__main__":
main()

Your MyListDropdownValue(MDDropdownMenu) class inherits from a MDDropdownMenu.
Then you make dropdown instance with
openlistdrop_down = MyDropdownValue(id)
Then you add that instance every time you "on_text" with
self.add_widget(listdropdown)
So you are adding multiple dropdowns.
In Kv try changing
on_text:
root.open_listdropdown(textfield_id)
To
on_validate:
root.open_listdropdown(textfield_id)
Then the user will need to hit enter before the list is made instead of with every letter added.

CheckBox Action Repeats in a KivyMD RecycleView Grid

When the checkbox for an item is clicked/unclicked in a recycleview grid, the click/unclick also automatically repeats for other data items in the grid. Why is this happening? The code below is a minimum working example. Thanks.
from kivy.lang import Builder
from kivy.uix.screenmanager import ScreenManager, Screen
from kivy.uix.recycleview import RecycleView
from kivy.properties import StringProperty, ListProperty
from kivy.clock import Clock
from kivymd.app import MDApp
from kivymd.uix.imagelist import SmartTile
from kivymd.uix.selectioncontrol import MDCheckbox
Builder.load_string("""
<Check>:
<GridTile>:
SmartTile:
source: root.tile
size_hint_y: None
height: '150dp'
Check:
<GridScreen>:
name: 'grid_screen'
RV:
id: rv
viewclass: 'GridTile'
RecycleGridLayout:
cols: 2
size_hint_y: None
default_size: 1, dp(150)
default_size_hint: 1, None
height: self.minimum_height
""")
class GridTile(Screen):
tile = StringProperty('')
class GridScreen(Screen):
pass
class RV(RecycleView):
data = ListProperty('[]')
def __init__(self, **kwargs):
super(RV, self).__init__(**kwargs)
self.cell_data()
def cell_data(self):
self.data = [{"tile": 'The Beatles'} for i in range(41)]
class Check(SmartTile):
def __init__(self, **kwargs):
super().__init__(**kwargs)
Clock.schedule_once(self.add_checkbox)
def add_checkbox(self, interval):
app = MDApp.get_running_app()
self.check = MDCheckbox(size_hint=(None, None), size=(48, 48))
self.check.bind(active=app.on_checkbox_active)
self._box_overlay.add_widget(self.check)
class ThisApp(MDApp):
def __init__(self, **kwargs):
super().__init__(**kwargs)
def build(self):
self.sm = ScreenManager()
self.sm.add_widget(GridScreen(name='grid_screen'))
return self.sm
def on_checkbox_active(self, checkbox, value):
if value:
print('The checkbox', checkbox, 'is active', 'and', checkbox.state, 'state')
else:
print('The checkbox', checkbox, 'is inactive', 'and', checkbox.state, 'state')
if __name__ == "__main__":
ThisApp().run()

Here is a modified version of your original posted code. This version works, but there is some interaction between GridTile instances (when you click on one check box, another GridTile appears to refresh itself). I have only seen this interaction with KivyMd. Writing a similar app without KivyMD does not display that odd interaction.
from functools import partial
from kivy.lang import Builder
from kivy.uix.screenmanager import ScreenManager, Screen
from kivy.uix.recycleview import RecycleView
from kivy.properties import StringProperty, ListProperty, NumericProperty, ObjectProperty
from kivy.clock import Clock
from kivymd.app import MDApp
from kivymd.uix.imagelist import SmartTile
from kivymd.uix.selectioncontrol import MDCheckbox
Builder.load_string("""
<GridTile>:
SmartTile:
source: root.tile
size_hint_y: None
height: '150dp'
Check:
id: ck
root_ref: root # creat reference to containing GridTile
<GridScreen>:
name: 'grid_screen'
RV:
id: rv
viewclass: 'GridTile'
RecycleGridLayout:
cols: 2
size_hint_y: None
default_size: 1, dp(150)
default_size_hint: 1, None
height: self.minimum_height
""")
class GridTile(Screen):
# properties to be set in the rv.data
tile = StringProperty('')
index = NumericProperty(-1)
cb_state = StringProperty('normal')
def __init__(self, **kwargs):
super(GridTile, self).__init__(**kwargs)
self.bind(cb_state=self.set_cb_state) # bind the cb_state property to set the state of the MDCheckBox
def set_cb_state(self, gridtile, cb_state_value):
self.ids.ck.check.state = cb_state_value # actually set the state of the MDCheckBox
class GridScreen(Screen):
pass
class RV(RecycleView):
data = ListProperty('[]')
def __init__(self, **kwargs):
super(RV, self).__init__(**kwargs)
self.cell_data()
def cell_data(self):
self.data = [{"tile": 'The Beatles', "index": i, "cb_state": 'normal'} for i in range(41)]
class Check(SmartTile):
root_ref = ObjectProperty(None) # reference to the containing GridTile (set by kv)
def __init__(self, **kwargs):
super().__init__(**kwargs)
Clock.schedule_once(self.add_checkbox)
def add_checkbox(self, interval):
app = MDApp.get_running_app()
self.check = MDCheckbox(size_hint=(None, None), size=(48, 48))
self.check.bind(on_press=partial(app.on_checkbox_press, self)) # bind to on_press to avoid possible looping when active is changed
self._box_overlay.add_widget(self.check)
class ThisApp(MDApp):
def __init__(self, **kwargs):
super().__init__(**kwargs)
def build(self):
self.sm = ScreenManager()
self.sm.add_widget(GridScreen(name='grid_screen'))
return self.sm
def on_checkbox_press(self, check, checkbox):
new_state = checkbox.state
# set checkbox state back to the default
checkbox.state = 'normal' # avoids setting checkbox state without data
rv = self.root.get_screen('grid_screen').ids.rv
rv.data[check.root_ref.index]['cb_state'] = new_state
rv.refresh_from_data() # set the state from data
if __name__ == "__main__":
ThisApp().run()
Th gist of the modifications is the adding of the index and cb_state properties to the GridTile class and to the data. The index property is just used as the index into the data when adjusting the data. And the cb_state is the state of the MDCheckbox. Since the MDCheckbox does not appear in the kv, there is no automatic binding if the cb_state property to the actual state of the MDChckbox, so that binding is explicitly created in the GridTile class. Also, the binding of the MDCheckbox to update the data is changed to bind to on_press, rather than on_active, since the active property will be changed by the RecycleView based on the data and could result in a looping effecet.

The RecycleView works by recycling a minimal number of instances of the viewclass, which is GridTile in your case. The RecycleView assigns properties to those instances of GridTile based on the entries in the data. If you change any properties of GridTile, or its children, that are not handled in the data, then the RecycleView is unaware of those changes and those changes remain in the recycled instances of GridTile. So, if you want the MDCheckBox state to be handled correctly, you must include it in your data as another property of GridTile. The fact that your MDCheckBox is not in your kv, makes this much more difficult to accomplish. This answers the why question.

usage of DragBehavior in Kivy

I'm new for python and kivy, and struggling with them.
I wanted to implement drag and drop function (a function that when a image is dragged to another image and dropped on it, do something.) with kivy.
What I want to do are the following three things;
know the id of the element that the user has been holding now.
know the id of the element that the user is on hover.
know the id of the element which was under the pointer when the user has dropped what he had.
I thought this would be useful to deal with them, so I wrote down the python script and .kivy file following. However, it dosen't work as I intended.
there are many problems which I don't know how to solve;
print(self.id) returns None.
Even though I am dragging only 1 element, on_touch_up prints None twice.
once you dragged and dropped a image, the image cannot be dragged anymore.
python file:
from kivy.app import App
from kivy.uix.image import Image
from kivy.uix.behaviors import DragBehavior
from kivy.properties import BooleanProperty
from kivy.properties import ObjectProperty
from kivy.factory import Factory
from kivy.core.window import Window
class HoverBehavior(object):
"""Hover behavior.
:Events:
`on_enter`
Fired when mouse enter the bbox of the widget.
`on_leave`
Fired when the mouse exit the widget
"""
hovered = BooleanProperty(False)
border_point = ObjectProperty(None)
'''Contains the last relevant point received by the Hoverable. This can
be used in `on_enter` or `on_leave` in order to know where was dispatched the event.
'''
def __init__(self, **kwargs):
self.register_event_type('on_enter')
self.register_event_type('on_leave')
Window.bind(mouse_pos=self.on_mouse_pos)
super(HoverBehavior, self).__init__(**kwargs)
def on_mouse_pos(self, *args):
if not self.get_root_window():
return # do proceed if I'm not displayed <=> If have no parent
pos = args[1]
# Next line to_widget allow to compensate for relative layout
inside = self.collide_point(*self.to_widget(*pos))
if self.hovered == inside:
# We have already done what was needed
return
self.border_point = pos
self.hovered = inside
if inside:
self.dispatch('on_enter')
else:
self.dispatch('on_leave')
def on_enter(self):
pass
def on_leave(self):
pass
Factory.register('HoverBehavior', HoverBehavior)
class DraggableImage(DragBehavior, HoverBehavior, Image):
def __init__(self, **args):
super(DraggableImage, self).__init__(**args)
self.source_file = ""
self.is_on_hover = False
def on_enter(self):
self.source_file = self.source
self.source = "green.png"
self.is_on_hover = True
print(self.id)
def on_leave(self):
self.source = self.source_file
self.is_on_hover = False
print(self.id)
def on_touch_up(self, touch):
if self.is_on_hover:
print(self.id)
class TestApp(App):
def build(self):
pass
if __name__ == '__main__':
TestApp().run()
test.kivy:
<DraggableImage>
drag_rectangle: self.x, self.y, self.width, self.height
drag_timeout: 10000000
drag_distance: 0
BoxLayout:
orientation: "horizontal"
DraggableImage:
id: "left_left"
source: "red.png"
DraggableImage:
id: "left_right"
source: "yellow.png"
DraggableImage:
id: "right_left"
source: "red.png"
DraggableImage:
id: "right_right"
source: "yellow.png"

Create a StringProperty named, name for example. Don't use id, because id is used in kv.
Change your class and kv as so:
from kivy.properties import StringProperty
class DraggableImage(DragBehavior, HoverBehavior, Image):
name = StringProperty("")
def __init__(self, **args):
super(DraggableImage, self).__init__(**args)
self.source_file = ""
self.is_on_hover = False
def on_enter(self):
self.source_file = self.source
self.source = "green.png"
self.is_on_hover = True
print(self.name)
def on_leave(self):
self.source = self.source_file
self.is_on_hover = False
print(self.name)
def on_touch_up(self, touch):
if self.is_on_hover:
print(self.name)
KV = """
<DraggableImage>:
drag_rectangle: self.x, self.y, self.width, self.height
drag_timeout: 10000000
drag_distance: 0
BoxLayout:
orientation: "horizontal"
DraggableImage:
name: "left_left"
source: "red.png"
DraggableImage:
name: "left_right"
source: "yellow.png"
DraggableImage:
name: "right_left"
source: "red.png"
DraggableImage:
name: "right_right"
source: "yellow.png"
"""

How to trigger an action once on overscroll in Kivy?

I have a ScrollView that's supposed to have an update feature when you overscroll to the top (like in many apps). I've found a way to trigger it when the overscroll exceeds a certain threshold, but it triggers it a lot of times, as the on_overscroll event is triggered on every movement. So is there a way to limit it?
My code looks like this:
from kivy.app import App
from kivy.uix.scrollview import ScrollView
from kivy.uix.gridlayout import GridLayout
from kivy.uix.button import Button
from kivy.effects.dampedscroll import DampedScrollEffect
class Effect(DampedScrollEffect):
def on_overscroll(self, *args):
super().on_overscroll(*args)
if self.overscroll < -50:
print('hey')
class TestApp(App):
def build(self):
sv = ScrollView(effect_cls = Effect,
size_hint_y = 0.2)
gl = GridLayout(cols = 1,
size_hint_y = None)
gl.bind(minimum_height = gl.setter('height'))
for i in range(5):
gl.add_widget(Button(text = str(i),
size_hint = (None, None)))
sv.add_widget(gl)
return sv
TestApp().run()
So, as you can see, when the overscroll goes beyond 50, it prints a simple message. But when you actually try it, you'll see that it prints it many times. What I want for it is to trigger an event, stay untriggerable for some time (like a second) and update the content. I've tried messing with boolean flags and Clock, but it didn't work. What could be done here?

I would use a stateful decorator here:
class call_control:
def __init__(self, max_call_interval):
self._max_call_interval = max_call_interval
self._last_call = time()
def __call__(self, function):
def wrapped(*args, **kwargs):
now = time()
if now - self._last_call > self._max_call_interval:
self._last_call = now
function(*args, **kwargs)
return wrapped
class Effect(DampedScrollEffect):
def on_overscroll(self, *args):
super().on_overscroll(*args)
if self.overscroll < -50:
self.do_something()
#call_control(max_call_interval=1)
def do_something(self):
print('hey')

I know this an old question but someone might find it useful
This is a sample from tshirtman's github gist
from threading import Thread
from time import sleep
from kivy.app import App
from kivy.lang import Builder
from kivy.factory import Factory
from kivy.clock import mainthread
from kivy.properties import ListProperty, BooleanProperty
KV = '''
FloatLayout:
Label:
opacity: 1 if app.refreshing or rv.scroll_y > 1 else 0
size_hint_y: None
pos_hint: {'top': 1}
text: 'Refreshing…' if app.refreshing else 'Pull down to refresh'
RecycleView:
id: rv
data: app.data
viewclass: 'Row'
do_scroll_y: True
do_scroll_x: False
on_scroll_y: app.check_pull_refresh(self, grid)
RecycleGridLayout:
id: grid
cols: 1
size_hint_y: None
height: self.minimum_height
default_size: 0, 36
default_size_hint: 1, None
<Row#Label>:
_id: 0
text: ''
canvas:
Line:
rectangle: self.pos + self.size
width: 0.6
'''
class Application(App):
data = ListProperty([])
refreshing = BooleanProperty()
def build(self):
self.refresh_data()
return Builder.load_string(KV)
def check_pull_refresh(self, view, grid):
max_pixel = 200
to_relative = max_pixel / (grid.height - view.height)
if view.scroll_y < 1.0 + to_relative or self.refreshing:
return
self.refresh_data()
def refresh_data(self):
Thread(target=self._refresh_data).start()
def _refresh_data(self):
self.refreshing = True
sleep(2)
self.append_data([
{'_id': i, 'text': 'hello {}'.format(i)}
for i in range(len(self.data), len(self.data) + 50)
])
self.refreshing = False
#mainthread
def append_data(self, data):
self.data = self.data + data
if __name__ == "__main__":
Application().run()

Kivy multiple selection with checkboxes

I'm trying to create a view using Kivy that has a list of options that are all selected by default, and the user can choose to deselect some entries (by clicking on the checkbox or anywhere on the row).
Clicking on the label part of the row item works, but I noticed that clicking on the checkbox doesn't change the selection which I can't work out how to solve (I tried a few different state bindings, I left them commented out in the example code)
Here is a quick example showing what I've tried.
from kivy.app import App
from kivy.properties import StringProperty, ListProperty
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.selectableview import SelectableView
from kivy.uix.togglebutton import ToggleButtonBehavior
from kivy.adapters.models import SelectableDataItem
from kivy.lang import Builder
Builder.load_string("""
#: import ListAdapter kivy.adapters.listadapter.ListAdapter
#: import Factory kivy.factory.Factory
<MyListItem>:
height: 50
on_state: root.is_selected = args[1] == "down"
state: "down" if root.is_selected else "normal"
BoxLayout:
spacing: 10
CheckBox:
on_state: root.is_selected = args[1] == "down"
state: "down" if root.is_selected else "normal"
# on_state: root.state = args[1]
# state: root.state
Label:
text: root.name
<Page>:
orientation: "vertical"
ListView:
id: LV
adapter: ListAdapter(data=root.data, cls=Factory.MyListItem, args_converter=root.args_converter, selection_mode="multiple", propagate_selection_to_data=True)
Button:
size_hint_y: None
text: "print selection"
on_press: print(LV.adapter.selection)
""")
class MyListItem(ToggleButtonBehavior, SelectableView, BoxLayout):
name = StringProperty()
def __repr__(self):
return "%s(name=%r)" % (type(self).__name__, self.name)
def on_state(self, me, state):
print me, state
if state == "down":
self.select()
else:
self.deselect()
# self.is_selected = state == "down"
class DataItem(SelectableDataItem):
def __init__(self, name, **kwargs):
super(DataItem, self).__init__(**kwargs)
self.name = name
def __repr__(self):
return "%s(name=%r, is_selected=%r)" % (type(self).__name__, self.name, self.is_selected)
class Page(BoxLayout):
data = ListProperty()
def __init__(self, **kwargs):
super(Page, self).__init__(**kwargs)
self.data = [DataItem("Item {}".format(i), is_selected=True) for i in range(10)]
def args_converter(self, index, data_item):
return {
"index": index,
"name": data_item.name,
}
class ExampleApp(App):
def build(self):
return Page()
if __name__ == "__main__":
ExampleApp().run()
I'm using Kivy v1.9.1-dev
Edit: I worked out how to get all the entries pre-selected, I've updated the code and took that part of the question out.

Just in case someone else has the the question I point to the right url:
You should consider the new RecycleView, which has all the functionality you request. Look here for a sample: Kivy: alternative to deprecated features