问题
I want to add an additional class to my kivy app that is just an info storage depot. I'm not sure where to do this or if this approach is even advised.
The app has multiple screens. Each screen allows the user to make a selection. The user's selection is what I want to store in the additional class. The additional class will store data then ultimately use MQTT to send the data out. Also, I wanted to keep the class definition in a separate file so I could organize the program into logically ordered chunks.
(keep in mind I'm sharing a small fraction of the code, but this should be representative enough to convey my question)
My kivy python code:
from kivy.app import App
from kivy.uix.floatlayout import FloatLayout
from kivy.uix.screenmanager import ScreenManager, Screen
from storage import Storage # <<========================== this is the addtional class
# Screen Manager
class MyScreenManager(ScreenManager):
pass
# Background Color
class BG(FloatLayout):
pass
class VendorScreen(Screen):
pass
class InvoiceScreen(Screen):
def __init__(self, **kwargs):
super(InvoiceScreen, self).__init__(**kwargs)
self.invoice = ''
def keyEntry(self, number): # ............ Digit Pressed
invoice = self.ids.invoice # ......... link to kivy Label
invoice.text += number # ............. append number to invoice
def keyBack(self): # ..................... Backspace
invoice = self.ids.invoice # ......... link to kivy Label
invoice.text = invoice.text[:-1] # ... remove last digit
def set_invoice(self):
invoice = self.ids.invoice
self.invoice = invoice.text
class MainControlScreen(Screen):
pass
# Main-Execution
class mySuperApp(App):
def build(self):
return MyScreenManager()
if __name__ == '__main__':
mySuperApp().run()
my kv code:
#:kivy 1.0.9
<MyScreenManager>:
VendorScreen: # ........ Incoming Delivery, Screen 2b
name: 'vendor_screen'
InvoiceScreen: # ........ .................. Screen 3b
name: 'invoice_screen'
MainControlScreen: # ... .................. Screen 4b
name: 'main_control_screen'
<BG>
AsyncImage:
source: 'img/screen1_background4.png'
size_hint: 1, 1
<VendorScreen>
BG:
FloatLayout:
Button:
text: 'name1'
color: 1.0, 0.6, 0.0, 1
font_size: 40
size_hint_x: 0.45
size_hint_y: 0.35
pos_hint: {'x': 0.03, 'y': 0.50}
on_release:
root.manager.transition.direction = 'left'
root.manager.current = 'invoice_screen'
Button:
text: 'name2'
color: 1.0, 0.6, 0.0, 1
font_size: 40
size_hint_x: 0.45
size_hint_y: 0.35
pos_hint: {'x': 0.52, 'y': 0.50}
on_release:
root.manager.transition.direction = 'left'
root.manager.current = 'invoice_screen'
Button:
text: 'name3'
color: 1.0, 0.6, 0.0, 1
font_size: 40
size_hint_x: 0.45
size_hint_y: 0.35
pos_hint: {'x': 0.03, 'y': 0.10}
on_release:
root.manager.transition.direction = 'left'
root.manager.current = 'invoice_screen'
Button:
text: 'name4'
color: 1.0, 0.6, 0.0, 1
font_size: 40
size_hint_x: 0.45
size_hint_y: 0.35
pos_hint: {'x': 0.52, 'y': 0.10}
on_release:
root.manager.transition.direction = 'left'
root.manager.current = 'invoice_screen'
<InvoiceScreen>
BG:
canvas:
Color:
rgba: 0.90, 0.90, 0.90, 0.5
Rectangle:
pos: (40, 295)
size: (320, 35)
Color:
rgba: 0, 0, 0, 1
Line:
points: 40, 295, 360, 295, 360, 330, 40, 330, 40, 295
width: 1
BoxLayout:
orientation: 'horizontal' # break it up into left / right
FloatLayout:
Label:
pos_hint: {'x':0, 'y':.25}
font_size: 30
text: 'Enter Invoice Number'
color: 0.1, 0.1, 1, 1
Label:
id: invoice
pos_hint: {'x':0, 'y':.15}
font_size: 30
text: '' # initially blank
color: 0, 0, 0, 1
GridLayout:
cols: 3 # number of columns
rows: 4 # number of rows
Button:
text: '1'
on_release: root.keyEntry('1')
Button:
text: '2'
on_release: root.keyEntry('2')
Button:
text: '3'
on_release: root.keyEntry('3')
Button:
text: '4'
on_release: root.keyEntry('4')
Button:
text: '5'
on_release: root.keyEntry('5')
Button:
text: '6'
on_release: root.keyEntry('6')
Button:
text: '7'
on_release: root.keyEntry('7')
Button:
text: '8'
on_release: root.keyEntry('8')
Button:
text: '9'
on_release: root.keyEntry('9')
Button:
text: '< DEL'
on_release: root.keyBack()
Button:
text: '0'
on_release: root.keyEntry('0')
Button:
text: 'Done'
on_release:
root.set_invoice()
root.manager.transition.direction = 'left'
root.manager.current = 'main_control_screen'
<MainControlScreen>
BG:
canvas:
Color:
rgba: 0, 0, 1, 1
Line:
points: 500, 180, 770, 180, 770, 450, 500, 450, 500, 180
width: 3
FloatLayout:
Label: # foreground
pos_hint: {'x': 0.30, 'y': 0.13}
font_size: 80
text: '5'
color: 1.0, 0.6, 0.0, 1
Button:
size_hint_x: 0.2
size_hint_y: 0.1
pos_hint: {'x': 0.05, 'y': 0.05}
text: 'Auto-Reject'
on_release:
root.manager.transition.direction = 'up'
root.manager.current = 'vendor_screen'
Button:
size_hint_x: 0.2
size_hint_y: 0.1
pos_hint: {'x': 0.75, 'y': 0.05}
text: 'Photo'
on_release:
root.manager.transition.direction = 'left'
root.manager.current = 'invoice_screen'
And finally my additional class:
from datetime import datetime, date
import calendar
class Storage(object):
def __init__(self):
self.invoice = 0
self.unit_name = ''
self.unit_number = ''
self.receiver = ''
self.vendor = ''
self.day = calendar.day_name[date.today().weekday()]
self.delivery_time = datetime.now()
self.package_condition = True
self.email = ''
self.location = ('32.0, -117.0',)
self.duration = 0
self.img = 'img.jpg'
So my question is, where and how do I use my addtional class 'Storage'? I want all the kivy classes to be able to access a single instance of it, but I cannot figure out how to do that.
I tried instantiating a class just before mySuperApp().run() but I cannot access it inside the other classes. I tried using global to access the instance, but that didn't work.
I thought about inheriting from the class, but I'm not sure how to do this... I started by inheriting from Storage in my different screens, however, that does not let me access a single instance where all my data is, rather I would have to pull instance variables from multiple classes to amass the full data set. Then I tried inheriting mySuperApp in Storage, then running the ScreenManager from Storage, but that didn't work. It ran, but I couldn't access the instance variables from the other classes. Maybe I need to keep inheriting from Storage in all the other classes?
I'm not sure how to approach this as the kivy part is only a fraction of the program. In the end I will need several additional classes, but I don't understand how or where to link these. Once I get the concept I will apply it to the other necessary classes, but I don't know where to start.
回答1:
You could use the ScreenManager to share data.
The ScreenManager will allways be parent of all the screens.
So here are three ways you can access the manager.
root.manager:
The Screen's all have an attribute called manager, which is the ScreenManager which this Screen is in. So you can access it from any screen like this.
root.parent:
The Widget's if they are in another widget will all have it's parent. In this case, the Screen's parent is the ScreenManager. So you can access it from any screen like this.
app.root:
Every app has a root. In this case the root of the app, is the ScreenManager. So you can access it from anywhere like this.
Try this example, with three buttons demonstrating this:
from kivy.app import App
from kivy.uix.screenmanager import Screen, ScreenManager
from kivy.lang import Builder
from kivy.properties import StringProperty
class MyScreenManager(ScreenManager):
shared_data = StringProperty("")
class Screen1(Screen):
pass
class Screen2(Screen):
pass
root = Builder.load_string('''
<Screen1>:
name: "screen1"
BoxLayout:
orientation: "vertical"
TextInput:
on_text:
root.manager.shared_data = self.text
Label:
text:
root.manager.shared_data
Button:
text: "Go to screen2"
on_release: root.manager.current = "screen2"
Button:
text: "root.manager.shared_data"
on_release:
print(root.manager.shared_data)
Button:
text: "root.parent.shared_data"
on_release:
print(root.parent.shared_data)
Button:
text: "app.root.shared_data"
on_release:
print(app.root.shared_data)
<Screen2>:
name: "screen2"
BoxLayout:
orientation: "vertical"
TextInput:
on_text:
root.manager.shared_data = self.text
Label:
text:
root.manager.shared_data
Button:
text: "Go to screen1"
on_release: root.manager.current = "screen1"
MyScreenManager:
Screen1:
Screen2:
''')
class MyApp(App):
def build(self):
return root
来源：https://stackoverflow.com/questions/45516622/kivy-using-addtional-class-to-store-data-from-multiple-screens