android - Kivy 按功能更新标签

Question

试图弄清楚与 setter 的绑定(bind)在 kivy 中是如何工作的。我发现 API 中的文档非常糟糕。他们非常期望他们的 kivy 引擎有大量假设知识。

无论如何，咆哮结束。这是我的代码。

    class ScreenOne(Screen):
        story = StringProperty('')
        def __init__ (self,**kwargs):
            super (ScreenOne, self).__init__(**kwargs)

            Buttonlayout = GridLayout(orientation='vertical',cols=1, spacing=2, size_hint_y=None)
            Buttonlayout.bind(minimum_height=Buttonlayout.setter('height'))

            btn = Button(text="change the text", size_hint_y=None, height=80,text_size=(350,None),font_size='12sp')
            btn.bind(on_press=partial(self.changer,"text has changed"))

            Buttonlayout.add_widget(btn)
            root.add_widget(Buttonlayout)
            self.add_widget(root)

        def changer(self,*args):

            self.story = args[0]
            self.manager.current = 'screen2'

    class ScreenTwo(Screen):

        def __init__(self,**kwargs):
            super (ScreenTwo,self).__init__(**kwargs)
            my_box1 = BoxLayout(orientation='vertical')
            L1 = Label(text=self.screenOne.story,font_size='24dp')
            L1.bind(self.L1.setter('text')= story)
            my_button1 = Button(text="Go to screen 1",size_hint_y=None, size_y=100)
            my_button1.bind(on_press=self.changer)

            my_box1.add_widget(self.L1)
            my_box1.add_widget(my_button1)
            self.add_widget(my_box1)

        def changer(self,*args):
            self.manager.current = 'screen1'

我的想法是，当我按下类 screenOne 中的按钮并更改屏幕时，它应该更改 screenTwo 中的标签。我认为最好的方法是使用 Properties，然后将标签绑定(bind)到 StringProperty 中的更改。我可以很好地更改故事中的字符串，如果我向它添加打印指令，我可以看到它发生了变化。这只是我遇到问题的标签更新。

我似乎无法让它工作。非常感谢您的帮助和指导。

Answer 1

请注意，仅使用 kv 语言就可以(几乎)完全实现所需的行为:

myapp.py:

from kivy.uix.screenmanager import ScreenManager, Screen
from kivy.properties import StringProperty, ObjectProperty
from kivy.uix.gridlayout import GridLayout
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.label import Label
from kivy.uix.button import Button
from kivy.app import App

class ScreenOne(Screen):
    story = StringProperty('')

    def changer(self,*args):
        self.story += args[0]
        self.manager.current = 'screen2'

class ScreenTwo(Screen):
    pass

class MyApp(App):
    pass

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

和my.kv:

ScreenManager:
    ScreenOne:
        id: screen_one
        name: 'screen1'
        GridLayout:
            orientation:'vertical'
            cols:1
            spacing:2
            size_hint_y:None
            on_minimum_height: self.setter('height')
            Button:
                text:"change the text"
                size_hint_y:None
                height: 80
                text_size: (350,None)
                font_size: '12sp'
                on_press: screen_one.changer("text ")
    ScreenTwo:
        name: 'screen2'
        BoxLayout:
            orientation: 'vertical'
            Label:
                id: L1
                text: screen_one.story
                font_size: '24dp'
            Button:
                text: "Go to screen 1"
                size_hint_y: None
                size_y:100
                on_press: root.current = 'screen1'

但是，如果您想使用Label 的setter，请更改MyApp 类定义:

class MyApp(App):
    def build(self):
        print self.root.ids
        S1 = self.root.ids['screen_one']
        L1 = self.root.ids['L1']
        S1.bind(story=L1.setter('text'))

并确保 Label 的 text 是静态的:text: 'start ...'。