Kivy使用kv文件中的ScreenManager

Question

我正在编写一个kivy程序/游戏。我以前做过一个，但总共只有一个屏幕。我已经开始开发一个新程序，并提出了实现Screen Manager的想法。我设法在python文件中构建了Screen Manager，但它不适合我的长期使用，我想尝试从.kv file中获得Screen Manager。

任何指导都将不胜感激，不确定我错过了什么。我看了这个问题v（Kivy-屏幕管理器-访问其他类中的属性），拼凑出我认为正确的内容，但仍然无法加载屏幕-我觉得这是一个简单的答案，我是盲目的。。。

main.py；

from kivy.app import App
from kivy.uix.screenmanager import ScreenManager, Screen, FadeTransition

class MenuScreen(Screen):
    pass
class NewGameScreen(Screen):
    pass
class LoadGameScreen(Screen):
    pass
class ASCIILifeApp(App):
    pass
if __name__ == "__main__":
    ASCIILifeApp().run()

ASCIILife.kv；

#: kivy 1.9
#: import ScreenManager kivy.uix.screenmanager.ScreenManager
#: import Screen kivy.uix.screenmanager.ScreenManager
#: import NewGameScreen screen
#: import LoadGameScreen screen
ScreenManager:
    id: screen_manager
    #transition: FadeTransition()
    MenuScreen:
        id: menu_screen
        name: 'MenuScreen'
        manager: 'screen_manager'
    NewGameScreen:
        id: newgame_screen
        name: 'NewGameScreen'
        manager: 'screen_manager'
    LoadGameScreen: 
        id: loadgame_screen
        name: 'LoadGameScreen'
        manager: 'screen_manager'
<MenuScreen>:
    BoxLayout:
        orientation: 'vertical'
        Label:
            text: 'ASCII Life'
            font_size: 50
        Button:
            text: 'New Game'
            font_size: 30
            on_release: app.root.current = 'newgame'
        Button:
            text: 'Load Game'
            font_size: 30
            on_release: app.root.current = 'loadgame'
        Button:
            text: 'Settings'
            font_size: 30
            on_release: app.root.current = 'something'
<NewGameScreen>:
    BoxLayout:
        orientation: 'vertical'
        BoxLayout:
            orientation: 'vertical'
            Label:
                text: 'Game Length in Days'
                font_size: 30
            BoxLayout:
                orientation: 'horizontal'
                ToggleButton:
                    text: '100'
                    state: 'down'
                    group: 'newgame_days'
                    font_size: 30
                ToggleButton:
                    text: '200'
                    group: 'newgame_days'
                    font_size: 30
            BoxLayout:
                orientation: 'horizontal'
                ToggleButton:
                    text: '365'
                    group: 'newgame_days'
                    font_size: 30
                ToggleButton:
                    text: '3650'
                    group: 'newgame_days'
                    font_size: 30
            ToggleButton:
                text: 'Unlimited'
                group: 'newgame_days'
                font_size: 30
        BoxLayout:
            orientation: 'vertical'
            size_hint: (1, .5)
            Label:
                text: 'Difficulty (Score Multiplier)'
                font_size: 30
            BoxLayout:
                orientation: 'horizontal'
                ToggleButton:
                    text: 'Easy (x1)'
                    state: 'down'
                    group: 'newgame_difficulty'
                    font_size: 30
                ToggleButton:
                    text: 'Medium (x2.5)'
                    group: 'newgame_difficulty'
                    font_size: 30
                ToggleButton:
                    text: 'Hard (x5)'
                    group: 'newgame_difficulty'
                    font_size: 30
<LoadGameScreen>:
    BoxLayout:
        orientation: 'vertical'
        Label:
            text: 'load a game'
            font_size: 30
        Widget:
            canvas:
                Ellipse:
                    pos: self.pos
                    size: self.size
        BoxLayout:
            Button:
                text: 'Menu'
                font_size: 30
                on_release: app.root.current = 'menu'
            Button:
                text: 'text'
                font_size: 30

编辑：截断的kv文件

Answer 1

答案是使用生成器来构建kv文件。我知道这很简单。下面的文件；

主.py

#!/usr/bin/kivy
from kivy.app import App
from kivy.lang import Builder
from kivy.uix.screenmanager import ScreenManager, Screen, FadeTransition
from kivy.properties import ObjectProperty

class MenuScreen(Screen):
    pass
class NewGameScreen(Screen):
    pass
class LoadGameScreen(Screen):
    pass
class ScreenManager(ScreenManager):
    pass
buildKV = Builder.load_file("ASCIILife.kv")
class ASCIILifeApp(App):
    def build(self):
        return buildKV
if __name__ == "__main__":
    ASCIILifeApp().run()

Answer 2

详细介绍Chazara的发现：

根据命名惯例重命名kv代码文件：

Kivy在中查找与您的应用程序类同名的Kv文件小写，如果以"App"结尾，则减去"App"。

从文档：如何加载kv语言

或者只需使用生成器函数显式：

Builder.load_file('path/to/file.kv')

Answer 3

要进一步阐述Chazara的发现：我用kivy 1.10.1dev0和Python 3.6测试了Chazara的代码；我得到一个错误说：

 kivy.uix.screenmanager.ScreenManagerException: No Screen with name "something".

为了修复它，我更改了.kv文件

[...]    
Button:
   text: 'New Game'
   font_size: 30
   on_release: app.root.current = 'newgame'
[...]

至：

[...]    
Button:
   text: 'New Game'
   font_size: 30
   on_release: app.root.current = 'NewGameScreen'
[...]

它引用了ScreenManager 中给出的NewGameScreen的名称

    ScreenManager:
[...]
         NewGameScreen:
            id: newgame_screen
            *name: 'NewGameScreen'*
            manager: 'screen_manager'