How to update Kivy labels dynamically after button is pressed - mysql

Question

I'm trying to make an app that uses data from MySQL server. So far I was doing fine, until I stumbled accross a need to update the Labels.
This is what I have so far:
from kivy.uix.button import Button
from kivy.lang import Builder
from kivy.uix.screenmanager import ScreenManager, Screen
from kivy.uix.label import Label
from kivy.uix.scrollview import ScrollView
from kivy.clock import Clock
import MySQLdb
class MainView(ScrollView):
def qchange(self):
query = 'SELECT * FROM `citiestovisit` ORDER BY `idcitiestovisit`'
self.db_data(query)
q = 'SELECT * FROM `citiestovisit` ORDER BY `Name`'
def db_data(self, query=q):
#vector = ListProperty()
vector = []
con = MySQLdb.connect(host="localhost", user="root", passwd="", db="cities")
cur = con.cursor()
cur.execute('SET NAMES `utf8`')
cur.execute(query)
result = cur.fetchall()
for row in result:
string = str(row[0]) + " " + str(row[1]) + " " + str(row[2])
vector.append(string)
print vector
return vector
def __init__(self, **kwargs):
kwargs['cols'] = 2
super(MainView, self).__init__(**kwargs)
GL = GridLayout(cols = 3, spacing=10, size_hint_y=None)
GL.bind(minimum_height=GL.setter('height'))
for row in self.db_data():
splitRow = row.split(" ")
for data in splitRow:
GL.add_widget(Label(text=data,size_hint_y=None, font_size='20sp'))
self.add_widget(GL)
Builder.load_string("""
<MenuScreen>:
BoxLayout:
GridLayout:
cols: 1
Button:
text: 'Goto settings'
on_press:
root.manager.transition.direction = 'left'
root.manager.current = 'settings'
Button:
text: 'Quit'
Label:
font_name: 'C:\Anonymous\Anonymous.ttf'
text: "picture here"
<SettingsScreen>:
""")
# Declare both screens
class MenuScreen(Screen):
pass
class SettingsScreen(Screen):
pass
ss = SettingsScreen(name='settings')
layout = BoxLayout(orientation='vertical')
BL = BoxLayout()
layout.add_widget(BL)
#Instance of a MainView class
MV = MainView()
def callback(instance):
sm.transition.direction = 'right'
sm.current = 'menu'
def callback2(instance):
MV.qchange()
btn = Button(text="Back to Menu")
btn.bind(on_press=callback)
btn.size_hint = (1, 0.3)
BL.add_widget(btn)
btn2 = Button(text="Sort by ID")
btn2.size_hint = (1, 0.3)
btn2.bind(on_press=callback2)
BL.add_widget(btn2)
layout.add_widget(MainView())
sublayout = GridLayout(cols=3)
sublayout.add_widget(Label(text="hello"))
sublayout.add_widget(Label(text="World"))
sublayout.add_widget(Label(text="Python"))
layout.add_widget(sublayout)
ss.add_widget(layout)
# Create the screen manager
sm = ScreenManager()
sm.add_widget(MenuScreen(name='menu'))
sm.add_widget(ss)
class MyApp(App):
def build(self):
return sm
if __name__ == '__main__':
MyApp().run()
I'm particularly interested in def qchange(self) mehod as it passes into def db_data(self, query=q) a new query; as a result request is sent to the database and an array of strings is returned. However, this array is not proccessed any further and labels in GL widget are not updated. I think I need to add the clock that would call the __init__ in MainView, but it's only a guess as I've also read about using properties (which I don't know how to use here as well)
I've eddited my code. Now it looks like this:
class MainView(ScrollView):
def qchange(self):
query = 'SELECT * FROM `citiestovisit` ORDER BY `idcitiestovisit`'
#self.db_data(query)
#LG = self.LabelsGrid(self.GL)
q = 'SELECT * FROM `citiestovisit` ORDER BY `Name`'
def db_data(self, query=q):
vector = []
con = MySQLdb.connect(host="localhost", user="root", passwd="", db="cities")
cur = con.cursor()
cur.execute('SET NAMES `utf8`')
cur.execute(query)
result = cur.fetchall()
for row in result:
string = str(row[0]) + " " + str(row[1]) + " " + str(row[2])
vector.append(string)
print vector
return vector
class LabelsGrid(GridLayout):
def __init__(self, **kwargs):
self.cols = 3
self.spacing = 10
self.size_hint_y = None
def show_labels(self, strings):
self.clear_widgets()
for row in strings:
splitRow = row.split(" ")
for data in splitRow:
label = Label(text=data, size_hint_y=None, font_size='20sp')
self.add_widget(label)
GL = LabelsGrid()
def __init__(self, **kwargs):
kwargs['cols'] = 2
super(MainView, self).__init__(**kwargs)
self.GL=self.LabelsGrid()
# GL = GridLayout(cols = 3, spacing=10, size_hint_y=None)
self.GL.bind(minimum_height=self.GL.setter('height'))
self.GL.show_labels(self.db_data(self.q))
self.add_widget(self.GL)
#self.GL.clear_widgets()
Builder.load_string("""
<MenuScreen>:
BoxLayout:
GridLayout:
cols: 1
Button:
text: 'Goto settings'
on_press:
root.manager.transition.direction = 'left'
root.manager.current = 'settings'
Button:
text: 'Quit'
Label:
font_name: 'C:\Anonymous\Anonymous.ttf'
text: "picture here"
<SettingsScreen>:
""")
# Declare both screens
class MenuScreen(Screen):
pass
class SettingsScreen(Screen):
pass
ss = SettingsScreen(name='settings')
layout = BoxLayout(orientation='vertical')
BL = BoxLayout()
layout.add_widget(BL)
#Instance of a MainView class
MV = MainView()
def callback(instance):
sm.transition.direction = 'right'
sm.current = 'menu'
def callback2(instance):
MV.qchange()
btn = Button(text="Back to Menu")
btn.bind(on_press=callback)
btn.size_hint = (1, 0.3)
BL.add_widget(btn)
btn2 = Button(text="Sort by ID")
btn2.size_hint = (1, 0.3)
btn2.bind(on_press=callback2)
BL.add_widget(btn2)
layout.add_widget(MainView())
sublayout = GridLayout(cols=3)
sublayout.add_widget(Label(text="hello"))
sublayout.add_widget(Label(text="World"))
sublayout.add_widget(Label(text="Python"))
layout.add_widget(sublayout)
ss.add_widget(layout)
# Create the screen manager
sm = ScreenManager()
sm.add_widget(MenuScreen(name='menu'))
sm.add_widget(ss)
class MyApp(App):
def build(self):
return sm
if __name__ == '__main__':
MyApp().run()
By adding
class LabelsGrid(GridLayout):
def __init__(self, **kwargs):
self.cols = 3
self.spacing = 10
self.size_hint_y = None
def show_labels(self, strings):
self.clear_widgets()
for row in strings:
splitRow = row.split(" ")
for data in splitRow:
label = Label(text=data, size_hint_y=None, font_size='20sp')
self.add_widget(label)
I wanted to add custom GridLayout according to a given piece of advice, however, now I get an error saying:
AttributeError: 'LabelsGrid' object has no attribute '_trigger_layout'
Any ideas on how to handle this?

Answer 1

Create a custom grid layout, let's say LabelsGrid, and in the class implement a method show_labels. Example:
class LabelsGrid(GridLayout):
def show_labels(self, strings):
self.clear_widgets()
for text in strings:
label = Label(text=text)
self.add_widget(label)
This way, each time you call the method with names of labels in a list, it will update itself.