python - 将按钮绑定(bind)到 .kv 文件中 .py 中的类方法

Question

我在上课时遇到问题，无论我做什么都会出错，请告诉我哪里错了。我一直在尝试在第一个屏幕上绑定(bind)一个按钮以在按下时打开弹出窗口，但出现此错误:

AttributeError: 'str' object has no attribute 'bind'
   File "C:\Users\Lara\Downloads\Kivy-1.9.0-py3.4-win32-x64\kivy34\kivy\lang.py", line 2012, in _apply_rule
     setattr(widget_set, key, value)
   File "kivy\weakproxy.pyx", line 22, in kivy.weakproxy.WeakProxy.__setattr__ (kivy\weakproxy.c:1189)
   File "kivy\properties.pyx", line 397, in kivy.properties.Property.__set__ (kivy\properties.c:4680)
   File "kivy\properties.pyx", line 429, in kivy.properties.Property.set (kivy\properties.c:5203)
   File "kivy\properties.pyx", line 484, in kivy.properties.Property.dispatch (kivy\properties.c:5852)
   File "kivy\_event.pyx", line 1168, in kivy._event.EventObservers.dispatch (kivy\_event.c:12154)
   File "kivy\_event.pyx", line 1074, in kivy._event.EventObservers._dispatch (kivy\_event.c:11451)
   File "C:\Users\Lara\Downloads\Kivy-1.9.0-py3.4-win32-x64\kivy34\kivy\uix\popup.py", line 190, in on_content
    self._container.add_widget(value)
   File "C:\Users\Lara\Downloads\Kivy-1.9.0-py3.4-win32-x64\kivy34\kivy\uix\boxlayout.py", line 210, in add_widget
     widget.bind(

.py文件相关部分:

from kivy.app import App
from kivy.uix.screenmanager import ScreenManager, Screen, FadeTransition
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.floatlayout import FloatLayout
from kivy.uix.widget import Widget
from kivy.uix.label import Label
from kivy.uix.button import Button
from kivy.core.image import Image
from kivy.graphics import Color, Rectangle
from kivy.uix.popup import Popup
from kivy.properties import NumericProperty, ReferenceListProperty
from kivy.properties import ObjectProperty
from kivy.lang import Builder
from kivy.uix.popup import Popup


class InstructionsPopup(Popup):
    pass

class StartScreen(Screen):

    def show_instructions(self):
        p = InstructionsPopup()
        p.open()

class GameScreen(Screen):
    pass

class RootScreen(ScreenManager):
    pass

class Main2App(App):
    def build(self):
        self.load_kv("main2.kv")
        return RootScreen()        

if __name__ == "__main__":
    Main2App().run()

和.kv文件:

#:import FadeTransition kivy.uix.screenmanager.FadeTransition

<StartScreen>:
    name: "start"
    FloatLayout:
        Button:
            id: play
            text: "Play!"
            on_release: root.manager.current = 'game'
        Button:
            id: how
            text: "How to play"
            on_press: self.parent.parent.show_instructions()

<GameScreen>:
    name: "game"
    FloatLayout:
        SnakeWidget:
        InfoWidget: 
        Button:
            id: menu
            text: "Menu"

<InstructionsPopup>:
    size_hint: 0.5, 0.5
    content: "You start the game by ... "
    title: "How to play"

<RootScreen>:
    id: screen_manager
    transition: FadeTransition() 
    StartScreen:
        name: "start"
    GameScreen:
        name: "game"

我还尝试像这样在 StartScreen 类中绑定(bind)按钮:

btn = self.ids.how
btn.bind(on_press=ShowInstructions())

但它一直告诉我 self 未定义。

还有什么我可以尝试的想法或我可能错的地方吗？

Answer 1

您的 kivy 文件中有两个编码错误。

<StartScreen>:
    name: "start"
    BoxLayout:
    #Change your layout here
    #  OR
    #give pos or pos_hint or size_hint if you want to give floatlayout
        Button:
            id: play
            text: "Play!"
            on_release: root.manager.current = 'game'
        Button:
            id: how
            text: "How to play"
            on_press: root.show_instructions()
            #First error was here

<InstructionsPopup>:
    size_hint: 0.5, 0.5
    title: "How to play"
    #You add the content in the popup, this way
    Button:
        text: "dismiss"
        on_release: root.dismiss()