如何使用 .py 中的属性更新 .kv 中的标签文本？

Question

我想使用 .kv 中的按钮更新我的班级 MainHero 中的值，并基于我班级中的属性 nick 我需要更新 .kv中的标签>。 我需要自动处理这个问题，因为许多其他属性会自动生成，所以 labels 需要更新。 这是我的代码的一部分：

from kivy.app import App
from kivy.uix.screenmanager import ScreenManager, Screen
from kivy.properties import *
from kivy.lang import Builder
from kivy.clock import Clock


class MainHero():
     def __init__(self):
          self.nick = "Player"

class FightScreen(Screen):
    def __init__(self, **kwargs):
        super(FightScreen, self).__init__(**kwargs)
        self.af_init = Clock.create_trigger(self._init)
        self.af_init()

    def _init(self, dt):
         self.app = App.get_running_app()
    
    def rename(self):
        self.app.main_hero.nick = "Renamed"


class ScreenManagement(ScreenManager):
    pass



class Design(App):
    def __init__(self, **kwargs):
        super(Design, self).__init__(**kwargs)
        self.main_hero = MainHero() # Tried main_hero = MainHero() too
        self.val = StringProperty(self.main_hero.nick)  # string

    # Construct app
    def build(self):
        # design constructor
        kv = Builder.load_file('AppDesign.kv')
        return kv

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

# Using kv 2.0
ScreenManagement:
    id: screen_manager
    FightScreen:
        name: 'FightScreen'
        manager: screen_manager
        id: fight_screen

<FightScreen>

FloatLayout:
     Label:
          text: app.val
          size_hint: .2, .2
          pos_hint: {'center_x': .5, 'center_y': .35}
     Button:
          size_hint: .2, .2
          pos_hint: {'center_x': .5, 'center_y': .5}
          on_press:
               root.rename()
          

可能通过properties/EventDispetcher. 在我尝试的许多情况下，参考 app.val 类似于 。 我尝试使用（可能是错误的）

class Aaa(EventDispetcher); apply_property(**kwargs) 我也想用ObjectProperty 做到这一点，我认为它是不同的，我不知道该怎么做。

编辑：

     def rename(self):
          self.app.main_hero.nick = "Renamed"
          self.app.main_hero.num += 1
          self.app.val = self.app.main_hero  # not working need replace
          # probably something here (replacement)

class MainHero():
     def __init__(self):
          self.nick = "Player"
          self.num = 1
.
.
.
class Design(App):
     val = ObjectProperty()

     def __init__(self, **kwargs):
        super(Design, self).__init__(**kwargs)
        self.main_hero = MainHero() # Tried main_hero = MainHero() too
        self.val = self.main_hero  # object

.
.
.
Label:
     text: app.val.nick
     size_hint: .2, .2
     pos_hint: {'center_x': .5, 'center_y': .35}
Label:
     text: str(app.val.num)
     size_hint: .2, .2
     pos_hint: {'center_x': .7, 'center_y': .7}

Answer 1

StringProperty 必须在类方法之外定义，如下所示：

class Design(App):
    val = StringProperty()  # defines the val property
    def __init__(self, **kwargs):
        super(Design, self).__init__(**kwargs)
        self.main_hero = MainHero()  # Tried main_hero = MainHero() too
        self.val = self.main_hero.nick  # set value of the property

然后，在您的rename() 方法中，您可以更改app.val 的值

def rename(self):
    self.app.main_hero.nick = "Renamed"
    self.app.val = self.app.main_hero.nick

如果您想直接在kv 中使用MainHero 类中的值，它们必须是Properties。但是要将这些属性变成Properties，MainHero 类必须是Widget 或至少是EventDispatcher，如下所示：

class MainHero(EventDispatcher):
    nick = StringProperty()
    num = NumericProperty()

    def __init__(self):
        self.nick = "Player"
        self.num = 1

Answer 2

您需要在kv文件中为标签指定一个ID，并将您要更改文本的操作引用到回调函数，然后以这种方式更改标签的文本。

kv:

MDLabel:
        id: number
        text: "1"
        halign: "center"
        pos_hint: {"center_x": .5, "center_y": .5}

py:

class Screen2(Screen, n):
    def set_number(self):
        self.ids.number.text = f"{n}"