kivy：屏幕切换时如何运行循环功能而不挂屏？

Question

我想要实现的目标：当屏幕从 ScreenOne 切换到 ScreenTwo 时，运行“while 循环”函数，直到 ScreenTwo 上的按钮被按下并中断循环。

此函数应该运行并接收来自连接到我的计算机的条形码扫描仪的输入（意思是，输入是条形码）并使用扫描的条形码数量更新 ScreenTwo 上的标签。

然后，一旦我没有要扫描的条形码，请按 ScreenTwo 上的“完成”按钮 - 这应该发送输入“999”以中断循环功能。

我如何尝试在屏幕切换时运行函数：使用'on_enter'

class ScreenTwo(Screen):
    def on_enter(self):
        getStatus()
        updatePoints()

我面临的问题：

1. 屏幕从 ScreenOne 切换到 ScreenTwo，并且函数运行（我看到它发生在 Mac 终端上）但无法按下 ScreenTwo 上的按钮（Mac 色轮旋转）。
2. 我还没有弄清楚如何让“完成”按钮将输入“999”发送到函数以中断循环。

如何解决 1？

我如何实现 2？

这里分别是 ScreenOne 和 ScreenTwo 的截图：

---

这是 returnStation2.py 文件

from kivy.app import App
from kivy.uix.screenmanager import ScreenManager, Screen
from kivy.properties import ObjectProperty


def getStatus():
    while True:
        answer = input('What is the box ID? ')
        if answer == 999: #LOOPS BREAK WHEN INPUT IS 999
            break
        elif type(answer) == int:
            do something
        else:
            print('Sorry I did not get that')

def updatePoints():
    do something

class ScreenManagement(ScreenManager):
    screen_one = ObjectProperty(None)
    screen_two = ObjectProperty(None)

class ScreenOne(Screen):
    member_status = ObjectProperty(None)

    def backspace(self, textString):
        newTextString = textString[0:-1]
        self.display.text = newTextString

    def getPoints(self, phoneNumber):
        self.manager.screen_two.member_status.text = phoneNumber

class ScreenTwo(Screen):
    input_text = ObjectProperty(None)

    def on_enter(self):
        getStatus()
        updatePoints()

    def clearField(self):
        self.manager.screen_one.input_text.text = ""

class ReturnStationLayout2App(App):

    def build(self):
        return ScreenManagement()


if __name__ == '__main__':
    ReturnStationLayout2App().run()

这里是returnStationLayout2.kv

“完成”按钮（在 ScreenTwo 中）位于脚本底部。

屏幕切换到ScreenTwo时无法按下。 并且我希望按下时可以输入'999'来打破正在运行的循环功能。

<ScreenManagement>:
    screen_one: screen_one
    screen_two: screen_two

    ScreenOne:
        id: screen_one
        name: 'menu'
    ScreenTwo:
        id: screen_two
        name: 'settings'

<CustButton@Button>:
    font_size: 32

<ScreenOne>:
    input_text : entry
    GridLayout:
        id: numberPad
        rows: 5
        padding: [300,200]
        spacing: 10

        # Where input is displayed
        BoxLayout:
            Label:
                text: "+65"
                font_size: 50
                size_hint: 0.2, 1
            TextInput:
                id: entry
                font_size: 50
                multiline: False
                padding: [20, ( self.height - self.line_height ) / 2]


        BoxLayout:
            spacing: 10
            CustButton:
                text: "1"
                on_press: entry.text += self.text
            CustButton:
                text: "2"
                on_press: entry.text += self.text
            CustButton:
                text: "3"
                on_press: entry.text += self.text
            CustButton:
                text: "DEL"
                on_press: root.backspace(entry.text)

        BoxLayout:
            spacing: 10
            CustButton:
                text: "4"
                on_press: entry.text += self.text
            CustButton:
                text: "5"
                on_press: entry.text += self.text
            CustButton:
                text: "6"
                on_press: entry.text += self.text
            CustButton:
                text: "AC"
                on_press: entry.text = ""

        BoxLayout:
            spacing: 10
            CustButton:
                text: "7"
                on_press: entry.text += self.text
            CustButton:
                text: "8"
                on_press: entry.text += self.text
            CustButton:
                text: "9"
                on_press: entry.text += self.text
            CustButton:
                text: "Enter" #HERE IS THE ENTER BUTTON
                on_press:
                    root.manager.transition.direction = 'left'
                    root.manager.transition.duration = 1
                    root.manager.current = 'settings'
                    root.getPoints(entry.text)

        BoxLayout:
            spacing: 10
            Label:
                text: ""
            CustButton:
                text: "0"
                on_press: entry.text += self.text
            Label:
                text: ""
            Label:
                text: ""

<ScreenTwo>:
    member_status: memberStatus
    BoxLayout:
        Label:
            id: memberStatus
            text: ''  
        GridLayout:
            rows: 3
            padding: [100,500]
            spacing: 10
            BoxLayout:
                Label:
                    text: "You have scanned:"
            BoxLayout:
                CustButton:
                    text: "Done" #THIS IS THE BUTTON I HOPE TO BE ABLE TO BREAK THE LOOP FUNCTION
                    on_press:
                        root.manager.transition.direction = "right"
                        root.manager.current = 'menu'
                        root.clearField()

Answer 1

解决方案

此答案基于问题下 cmets 部分中的讨论。下面的代码是在假设扫描器在扫描条形码时发送特定信号的情况下编写的。总体思路是在发送该信号后运行一个函数。

时钟周期

我建议熟悉 kivy 的 Clock 对象。可以创建一个侦听器函数来检查信号是否每 n 秒发送一次。准确地说，假设您想在检测到信号后运行process() 函数。我们还声明一个变量scanned 来存储条形码是否成功扫描的信息，并创建一个侦听器来检查信号是否已发送（因此检查scanned 变量是否包含True）。以下代码示例将每 2 秒的 scanned 变量设置为 True 以模拟扫描行为。

from kivy.app import App
from kivy.clock import Clock
from kivy.uix.button import Button
from kivy.uix.screenmanager import Screen

# Define constants and the scanned variable, for easy example
INTERVAL = 0.01
scanned = False


# Process method runs every 0.01 seconds, note the use of dt argument (explained in docs)
def process(dt):
    # Retrieve the global variable, for easy example
    global scanned
        
    # Check if scanned, note setting scanned to False once an item was scanned.
    # Here you can also check the uniqueness of the scanned barcode (to avoid having the same barcode processed many times)
    if scanned is True:
        print("Scanned! Processing the data and setting scanned to False.")
        scanned = False
    else:
        print("Not scanned yet!")


# Mimic scanning behaviour
def scan(dt):
    # Retrieve the global variable and set it to true 
    global scanned
    scanned = True


class Main(App):

    def __init__(self):
        super(Main, self).__init__()
        
        # Schedule the functions to be called every n seconds
        Clock.schedule_interval(process, INTERVAL)
        Clock.schedule_interval(scan, INTERVAL*200)

    def build(self):
        # Display screen with a single button for easy example
        scr = Screen()
        btn = Button(text="You can press me but nothing will happen!")
        scr.add_widget(btn)
        return scr


if __name__ == '__main__':
    Main().run()

输出：

Not scanned yet!
.
.
.
Not scanned yet!
Scanned! Processing the data and setting scanned to False.