kivy bind() 正好采用 2 个位置参数（给定 0）

Question

我正在使用 kivy 在 python() 中构建电梯系统 GUI。我正在编写它，以便当按下楼层的向上按钮时，将调用一个函数，该函数将生成一个请求并将其发送到系统。我现在正在尝试使用以下方法将该功能绑定到向上按钮：

self.floor1.up_button.bind(on_press=self.up_pressed(1))

编译器给我发了一个错误：

TypeError: bind() takes exactly 2 positional arguments (0 given)

有解决办法吗？ Python初学者，如果这是一个非常简单的问题，请道歉。

下面是.py文件中的相关代码：

from kivy.uix.label import Label
from kivy.uix.button import Button
from kivy.app import App
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.gridlayout import GridLayout
from kivy.properties import ObjectProperty
from random import randint

class FloorRequestStatus:
    up = 0
    down = 1

class Request:
    def __init__(self, start, status, destination, waiting_time):
        self.start = start
        self.status = status
        self.destination = destination
        self.waiting_time = waiting_time

class Floor(GridLayout):
    up_count = NumericProperty(0)
    down_count = NumericProperty(0)
    floor_index = NumericProperty(0)

    up_button = ObjectProperty(Button)
    down_button = ObjectProperty(Button)

class FloorSystem(BoxLayout):
    floor1 = ObjectProperty(Floor)  # type:Floor
    floor2 = ObjectProperty()
    floor3 = ObjectProperty()
    floor4 = ObjectProperty()

    floors = [floor1, floor2, floor3, floor4]

    request_queue = []

    def __init__(self, **kwargs):
        super(FloorSystem, self).__init__(**kwargs)
        self.floor1.up_button.bind(on_press=self.up_pressed(1))

    def generate_destination(self, floor_index, status):
        if status == FloorRequestStatus.up:
            return randint(floor_index + 1, 20)
        if status == FloorRequestStatus.down:
            return randint(0, floor_index - 1)

    def up_pressed(self, floor_index):
        a_request = Request(floor_index, FloorRequestStatus.up,
                        self.generate_destination(floor_index,FloorRequestStatus.up), 0)
        self.request_queue.append(a_request)

这些是.kv文件中的相关代码：

#:kivy 1.0.9

<Floor@GridLayout>
    floor_index: 0
    pos: 200,200
    rows: 1
    spacing: 1

    GridLayout:
        size_hint_x: 35
        cols: 1

        Button:
            id: up_button
            size_hint_y: 50
            text: 'up'
            on_press: root.up_count += 1

        Button:
            id:down_button
            size_hint_y: 50
            text: 'down'
            on_press: root.down_count += 1

    Label:
        id: floor_label
        size_hint_x: 65
        text: root.label_text
        background_color: 1,1,1,1
        text: str(root.floor_index) + 'F (' + str(root.up_count) + ',' + str(root.down_count) + ')'

        canvas:
            Color:
                rgba: .3, .5, 1, .4
            Rectangle:
                size: self.size
                pos: self.pos

<FloorSystem>
    floor1: floor1
    floor2: floor2
    floor3: floor3
    floor4: floor4

    orientation: 'vertical'
    size_hint: None, None
    width: 160
    height: 700
    spacing: 2

    Floor:
        id: floor4
        floor_index: 4

    Floor:
        id: floor3
        floor_index: 3

    Floor:
        id: floor2
        floor_index: 2

    Floor:
        id: floor1
        floor_index: 1

Answer 1

参考原代码会遇到如下错误。

错误

         self.floor1.up_button.bind(on_press=self.up_pressed(1))
     TypeError: descriptor 'bind' of 'kivy._event.EventDispatcher' object needs an argument

说明

发生上述错误是因为 up_button 连接到 Button 类 而没有连接到 Button 对象。如果您将打印语句 print(self.floor1.up_button) 插入您的程序中，您将看到不同之处。

Event dispatcher

通常，属性回调使用 2 个参数（对象和属性的新值）调用，事件回调使用一个参数（对象）。

解决方案

Python 脚本 - 删除按钮

替换：

up_button = ObjectProperty(Button)
down_button = ObjectProperty(Button)

与：

up_button = ObjectProperty(None)
down_button = ObjectProperty(None)

kv 文件 - 连接对象属性

<Floor@GridLayout>
    up_button: up_button
    down_button: down_button

    floor_index: 0
    ...

按钮绑定

至于绑定，可以使用偏函数。

self.floor1.up_button.bind(on_press=partial(self.up_pressed, 1))

示例

main.py

​​>

from kivy.uix.label import Label
from kivy.uix.button import Button
from kivy.app import App
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.gridlayout import GridLayout
from kivy.properties import ObjectProperty, NumericProperty
from random import randint
from functools import partial


class FloorRequestStatus:
    up = 0
    down = 1


class Request:
    def __init__(self, start, status, destination, waiting_time):
        self.start = start
        self.status = status
        self.destination = destination
        self.waiting_time = waiting_time


class Floor(GridLayout):
    up_count = NumericProperty(0)
    down_count = NumericProperty(0)
    floor_index = NumericProperty(0)

    up_button = ObjectProperty(None)
    down_button = ObjectProperty(None)


class FloorSystem(BoxLayout):
    floor1 = ObjectProperty(None)
    floor2 = ObjectProperty(None)
    floor3 = ObjectProperty(None)
    floor4 = ObjectProperty(None)

    floors = [floor1, floor2, floor3, floor4]

    request_queue = []

    def __init__(self, **kwargs):
        super(FloorSystem, self).__init__(**kwargs)
        self.floor1.up_button.bind(on_press=partial(self.up_pressed, 1))

    def generate_destination(self, floor_index, status):
        if status == FloorRequestStatus.up:
            return randint(floor_index + 1, 20)
        if status == FloorRequestStatus.down:
            return randint(0, floor_index - 1)

    def up_pressed(self, floor_index):
        a_request = Request(floor_index, FloorRequestStatus.up,
                            self.generate_destination(floor_index, FloorRequestStatus.up), 0)
        self.request_queue.append(a_request)


class TestApp(App):
    def build(self):
        return FloorSystem()


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

test.kv

#:kivy 1.10.0

<Floor@GridLayout>
    up_button: up_button
    down_button: down_button

    floor_index: 0
    pos: 200,200
    rows: 1
    spacing: 1

    GridLayout:
        size_hint_x: 35
        cols: 1

        Button:
            id: up_button
            size_hint_y: 50
            text: 'up'
            on_press: root.up_count += 1

        Button:
            id:down_button
            size_hint_y: 50
            text: 'down'
            on_press: root.down_count += 1

    Label:
        id: floor_label
        size_hint_x: 65
        text: root.label_text
        background_color: 1,1,1,1
        text: str(root.floor_index) + 'F (' + str(root.up_count) + ',' + str(root.down_count) + ')'

        canvas:
            Color:
                rgba: .3, .5, 1, .4
            Rectangle:
                size: self.size
                pos: self.pos

<FloorSystem>
    floor1: floor1
    floor2: floor2
    floor3: floor3
    floor4: floor4

    orientation: 'vertical'
    size_hint: None, None
    width: 160
    height: 700
    spacing: 2

    Floor:
        id: floor4
        floor_index: 4

    Floor:
        id: floor3
        floor_index: 3

    Floor:
        id: floor2
        floor_index: 2

    Floor:
        id: floor1
        floor_index: 1

输出