在 kivy 上 class 之间传递值时为空白值？

Question

在这种情况下，我将在 class 或 Screen 之间传递值，但打印时这些值是空的。这是我的 py 代码：

import kivy
from kivy.app import App
from kivy.uix.widget import Widget
from kivy.uix.gridlayout import GridLayout
from kivy.uix.button import Button
from kivy.uix.textinput import TextInput
from kivy.uix.label import Label
from kivy.properties import ObjectProperty
from kivy.uix.screenmanager import ScreenManager, Screen
from kivy.lang import Builder


class MyLayout(Screen):
    pstd=ObjectProperty(None)
    def save():
        pass

    def calculate(self):
        pstd=self.pstd.text
        pres=self.pres.text
        tres=self.tres.text
        tsep=self.tsep.text
        psep=self.psep.text
        api=self.api.text
        dg=self.sg.text
        pb=self.pb.text
        co2=self.co2.text
        h2s=self.h2s.text
        n2=self.n2.text
        tds=self.tds.text
        if(self.sat.state == "down"):
            cond = 2
        else :
            cond = 1
        print(pstd)
        return pstd
        

    
class MyLayout2(Screen):
    def press(self):
        print(App.get_running_app().my_layout.calculate())
        


    
class WindowManager(ScreenManager):
    pass
kv = Builder.load_file("tubes.kv")

class TubesApp(App):
    my_layout = MyLayout()
    def build(self):
        return kv

if __name__ == "__main__":
    TubesApp().run()

这是我的 kv 代码：

WindowManager:
    MyLayout:
    MyLayout2:

<MyLayout>:
    name: "main"
    free:free
    sat:sat
    pstd:pstd
    tres:tres
    pres:pres
    tsep:tsep
    psep:psep
    api:api
    sg:sg
    pb:pb
    co2:co2
    h2s:h2s
    n2:n2
    tds:tds
    btn:btn
    background_color : 71/255,213/255,223/255,1
    canvas.before:
        Color :
            rgba : self.background_color
        Rectangle :
            size : self.size
            pos : self.pos
    FloatLayout :
        size : root.width,root.height
        Label :
            text : "PVT Calculator"
            font_size : 20
            size_hint : (None,None)
            size : 400,100
            color: 1,1,1,1
            pos_hint : {"center_x":0.5,"top" : 1}
            background_color : (35/255,135/255,142/255,1)
            canvas.before:
                Color :
                    rgba : self.background_color
                Rectangle :
                    size : self.size
                    pos : self.pos
        Label :
            text : "Oil Data"
            font_size : 20
            size_hint : (0.5,0.09)
            color: 0.3,0.4,0.5,1
            pos_hint : {"center_x":0.25,"top" : 0.8}
            background_color : (71/255,220/255,141/255,1)
            canvas.before:
                Color :
                    rgba : self.background_color
                Rectangle :
                    size : self.size
                    pos : self.pos

        Label :
            text : "API"
            font_size : 12
            size_hint : (0.25,0.04)
            color: 1,1,1,1
            pos_hint : {"x":0, "top":0.712}
            background_color : (5/255,95/255,53/255,1)
            canvas.before:
                Color :
                    rgba : self.background_color
                Rectangle :
                    size : self.size
                    pos : self.pos
        TextInput :
            id:api
            multiline:False
            font_size : 12
            size_hint : (0.25,0.04)
            pos_hint : {"x":0.25, "top":0.712}

        Label :
            text : "Saturation pressure"
            font_size : 12
            size_hint : (0.25,0.04)
            color: 1,1,1,1
            pos_hint : {"x":0, "top":0.672}
            background_color : (6/255,124/255,69/255,1)
            canvas.before:
                Color :
                    rgba : self.background_color
                Rectangle :
                    size : self.size
                    pos : self.pos
        TextInput :
            id:pb
            multiline:False
            font_size : 12
            size_hint : (0.25,0.04)
            pos_hint : {"x":0.25, "top":0.672}

        Label :
            text : "Spesific Gravity"
            font_size : 12
            size_hint : (0.25,0.04)
            pos_hint : {"x":0, "top":0.632}
            color: 1,1,1,1
            background_color : (8/255,152/255,85/255,1)
            canvas.before:
                Color :
                    rgba : self.background_color
                Rectangle :
                    size : self.size
                    pos : self.pos
        TextInput : 
            id:sg
            multiline:False
            font_size : 12
            size_hint : (0.25,0.04)
            pos_hint : {"x":0.25, "top":0.632}

        Label : 
            text : "Non-Hydrocarbon Component"
            font_size : 20
            size_hint : (0.5,0.09)
            color: 0.3,0.4,0.5,1
            pos_hint : {"center_x":0.75,"top" : 0.8}
            background_color : (14/255,195/255,110/225,1)
            canvas.before:
                Color :
                    rgba : self.background_color
                Rectangle :
                    size : self.size
                    pos : self.pos
        Label :
            text : "CO2"
            font_size : 12
            size_hint : (0.25,0.04)
            color: 1,1,1,1
            pos_hint : {"x":0.5, "top":0.712}
            background_color : (5/255,95/255,53/255,1)
            canvas.before:
                Color :
                    rgba : self.background_color
                Rectangle :
                    size : self.size
                    pos : self.pos
        TextInput : 
            id:co2
            multiline:False
            font_size : 12
            size_hint : (0.25,0.04)
            pos_hint : {"x":0.75, "top":0.712}

        Label :
            text : "H2S"
            font_size : 12
            size_hint : (0.25,0.04)
            color: 1,1,1,1
            pos_hint : {"x":0.5, "top":0.672}
            background_color : (6/255,124/255,69/255,1)
            canvas.before:
                Color :
                    rgba : self.background_color
                Rectangle :
                    size : self.size
                    pos : self.pos
        TextInput : 
            id:h2s
            multiline:False
            font_size : 12
            size_hint : (0.25,0.04)
            pos_hint : {"x":0.75, "top":0.672}

        Label :
            text : "N2"
            font_size : 12
            size_hint : (0.25,0.04)
            color: 1,1,1,1
            pos_hint : {"x":0.5, "top":0.632}
            background_color : (8/255,152/255,85/255,1)
            canvas.before:
                Color :
                    rgba : self.background_color
                Rectangle :
                    size : self.size
                    pos : self.pos
        TextInput : 
            id:n2
            multiline:False
            font_size : 12
            size_hint : (0.25,0.04)
            pos_hint : {"x":0.75, "top":0.632}

        Label :
            text : "Reservoir and Separator Data"
            font_size : 20
            size_hint : (0.5,0.09)
            color: 0.3,0.4,0.5,1
            pos_hint : {"center_x":0.25,"top" : 0.5}
            background_color : (14/255,195/255,110/225,1)
            canvas.before:
                Color :
                    rgba : self.background_color
                Rectangle :
                    size : self.size
                    pos : self.pos
        Label :
            text : "Reservoir Temperature"
            font_size : 12
            size_hint : (0.25,0.04)
            pos_hint : {"x":0, "top":0.41}
            color: 1,1,1,1
            background_color : (5/255,95/255,53/255,1)
            canvas.before:
                Color :
                    rgba : self.background_color
                Rectangle :
                    size : self.size
                    pos : self.pos
        TextInput : 
            id:tres
            multiline:False
            font_size : 12
            size_hint : (0.25,0.04)
            pos_hint : {"x":0.25, "top":0.41}

        Label :
            text : "Initial Reservoir pressure"
            font_size : 12
            size_hint : (None,None)
            size : 200,25
            color: 1,1,1,1
            pos : 0,200
            background_color : (6/255,124/255,69/255,1)
            canvas.before:
                Color :
                    rgba : self.background_color
                Rectangle :
                    size : self.size
                    pos : self.pos
        TextInput : 
            id:pres
            multiline:False
            font_size : 12
            size_hint : (None,None)
            size : 200,25
            pos : 200,200

        Label :
            text : "Separator Temperature"
            font_size : 12
            size_hint : (None,None)
            size : 200,25
            color: 1,1,1,1
            pos : 0,175
            background_color : (8/255,152/255,85/255,1)
            canvas.before:
                Color :
                    rgba : self.background_color
                Rectangle :
                    size : self.size
                    pos : self.pos
        TextInput : 
            id:tsep
            multiline:False
            font_size : 12
            size_hint : (None,None)
            size : 200,25
            pos : 200,175

        Label :
            text : "Separator pressure"
            font_size : 12
            size_hint : (None,None)
            size : 200,25
            color: 1,1,1,1
            pos : 0,150
            background_color : (9/255,181/255,101/255,1)
            canvas.before:
                Color :
                    rgba : self.background_color
                Rectangle :
                    size : self.size
                    pos : self.pos
        TextInput :
            id:psep
            multiline:False
            font_size : 12
            size_hint : (None,None)
            size : 200,25
            pos : 200,150

        Label :
            text : "Standard pressure"
            font_size : 12
            size_hint : (None,None)
            size : 200,25
            color: 1,1,1,1
            pos : 0,125
            background_color : (10/255,209/255,116/255,1)
            canvas.before:
                Color :
                    rgba : self.background_color
                Rectangle :
                    size : self.size
                    pos : self.pos
        TextInput : 
            id:pstd
            multiline:False
            font_size : 12
            size_hint : (None,None)
            size : 200,25
            pos : 200,125

        Label :
            text : "Water Formation Data"
            font_size : 20
            size_hint : (0.5,0.09)
            color: 0.3,0.4,0.5,1
            pos_hint : {"center_x":0.75,"top" : 0.5}
            background_color : (71/255,220/255,141/255,1)
            canvas.before:
                Color :
                    rgba : self.background_color
                Rectangle :
                    size : self.size
                    pos : self.pos
            Label :
                size_hint : (None,None)
                size : 400,125
                color: 0.3,0.4,0.5,1
                pos: 400,125
                background_color : (5/255,95/255,53/255,1)
                canvas.before:
                    Color :
                        rgba : self.background_color
                    Rectangle :
                        size : self.size
                        pos : self.pos

            Label :
                text : "Condition"
                font_size : 12
                size_hint : (None,None)
                size : 400,25
                color: 1,1,1,1
                pos : 400,225
                background_color : (6/255,124/255,69/255,1)
                canvas.before:
                    Color :
                        rgba : self.background_color
                    Rectangle :
                        size : self.size
                        pos : self.pos
            ToggleButton :
                id:sat
                text : "Gas-Saturated Brine"
                size_hint : (None,None)
                size : 180, 60
                pos : 420, 155
                group : 'Condition'
     
            ToggleButton :
                id:free
                text : "Gas-Free Brine"
                size_hint : (None,None)
                size : 180, 60
                pos : 610, 155
                group : 'Condition'
                state: "normal" 
                    

            Label :
                text : "Total Dissolved Solid"
                font_size : 12
                size_hint : (None,None)
                size : 200,25
                color: 1,1,1,1
                pos : 400,125
                background_color : (10/255,209/255,116/255,1)
                canvas.before:
                    Color :
                        rgba : self.background_color
                    Rectangle :
                        size : self.size
                        pos : self.pos
            TextInput : 
                id:tds
                multiline:False
                font_size : 12
                size_hint : (None,None)
                size : 200,25
                pos : 600,125
        
        Button :
            id:btn
            text : "CALCULATE"
            size_hint : (None,None)
            size : 180, 60
            pos_hint : {"center_x":0.5,"y":0.05}
            on_press : root.calculate()
            on_release : app.root.current = "second"

<MyLayout2>:

    name : "second"
    ubah:ubah
    GridLayout :
        cols : 1
        Label :
            id:ubah
            text : "test"
        Button :
            text : "Back"
            on_press : root.press()
            on_release : app.root.current = "main"

我试图在传递给另一个 class 之前打印它，所以它在其中时有值 class 但在更改 class 时为空，谁能帮我解决这个问题我是基维新人

Answer 1

该值为空，因为该函数无法看到当前运行 class 具有您想要的值。如果您想查看您所做的更改而不是初始值，您需要让 classes 看到彼此。

首先获取您的应用程序运行，然后转到其屏幕管理器。在那里你可以得到你想要的值的屏幕，然后执行函数。

class MyLayout2(Screen):
    def press(self):
        running = App.get_running_app()
        manager = running.root
        layout1 = manager.get_screen('main')
        print(layout1.calculate())
        # Or just print(App.get_running_app().root.get_screen('main').calculate())

在 kivy 上 class 之间传递值时为空白值？

Blank value when passing values between class on kivy?

python

oop

kivy

kivy-language

kivymd