當窗口調整大小時調整文本大小Python/Kivy

Question

我有一個Python/Kivy應用程序，我正在創建，並且我正在嘗試在窗口大小調整時調整文本大小。我查了一下，但沒有找到和我預期的完全一樣的東西。我想我會將on_resize綁定到調整文本大小的函數，但是我收到了很多錯誤。這是相關的代碼。

class MainScreen(Screen): 
    def __init__(self, **kwargs): 
     super(MainScreen, self).__init__(**kwargs) 
     self.font_size = 25 

class MainApp(App): 
    def build(self): 
     def win_cb(window, width, height): 
      new_size = sqrt(width**2 + height**2)/40.6 
      MainScreen().font_size = new_size 
     Window.bind(on_resize=win_cb) 

我還要提到的是，在一個.kv文件我有這樣的事情

<MainScreen>: 
    Label: 
     text: "Text here" 
     pos_hint: {"x": -0.15, "y": 0.05} 
     font_size: root.font_size*80/25 

在運行時，它工作正常，但是當我調整窗口的大小，我得到錯誤的巨大列，看樣子與MainScreen相關的沒有屬性font_size。

這是錯誤消息：

Traceback (most recent call last): 
    File "/usr/lib/python3.4/site-packages/kivy/lang.py", line 1649,  in create_handler 
    return eval(value, idmap) 
    File "main.kv", line 46, in <module> 
    font_size: root.font_size 
    File "kivy/weakproxy.pyx", line 19, in kivy.weakproxy.WeakProxy.__getattr__ (kivy/weakproxy.c:1101) 
AttributeError: 'MainScreen' object has no attribute 'font_size' 

During handling of the above exception, another exception occurred: 

Traceback (most recent call last): 
    File "/usr/lib/python3.4/site-packages/kivy/lang.py", line 2011, in _apply_rule 
value, rule, rctx['ids']) 
    File "/usr/lib/python3.4/site-packages/kivy/lang.py", line 1654, in create_handler 
cause=tb) 
kivy.lang.BuilderException: Parser: File "main.kv", line 46: 
... 
     44:  text: "Simplify Fraction" 
     45:  pos_hint: {"right": 1, "top":0.2} 
>> 46:  font_size: root.font_size 
     47: 
     48: 
... 
AttributeError: 'MainScreen' object has no attribute 'font_size' 
    File "/usr/lib/python3.4/site-packages/kivy/lang.py", line 1649, in create_handler 
    return eval(value, idmap) 
    File "main.kv", line 46, in <module> 
    font_size: root.font_size 
    File "kivy/weakproxy.pyx", line 19, in  kivy.weakproxy.WeakProxy.__getattr__ (kivy/weakproxy.c:1101) 


During handling of the above exception, another exception occurred: 

Traceback (most recent call last): 
    File "/home/onehitfinish/Downloads/Gregulator Files/test.py", line 88, in <module> 
    MainApp().run() 
    File "/usr/lib/python3.4/site-packages/kivy/app.py", line 824, in run 
    runTouchApp() 
    File "/usr/lib/python3.4/site-packages/kivy/base.py", line 487, in runTouchApp 
    EventLoop.window.mainloop() 
    File "/usr/lib/python3.4/site-packages/kivy/core/window/window_sdl2.py", line 525, in mainloop 
    self._mainloop() 
    File "/usr/lib/python3.4/site-packages/kivy/core/window/window_sdl2.py", line 290, in _mainloop 
    EventLoop.idle() 
    File "/usr/lib/python3.4/site-packages/kivy/base.py", line 327, in idle 
    Clock.tick() 
    File "/usr/lib/python3.4/site-packages/kivy/clock.py", line 483, in tick 
    self._process_events() 
    File "/usr/lib/python3.4/site-packages/kivy/clock.py", line 615, in _process_events 
    event.tick(self._last_tick, remove) 
    File "/usr/lib/python3.4/site-packages/kivy/clock.py", line 374, in tick 
    ret = callback(self._dt) 
    File "/usr/lib/python3.4/site-packages/kivy/core/window/window_sdl2.py", line 188, in create_window 
    super(WindowSDL, self).create_window() 
    File "/usr/lib/python3.4/site-packages/kivy/core/window/__init__.py", line 779, in create_window 
    self.dispatch('on_resize', *self.system_size) 
    File "kivy/_event.pyx", line 695, in kivy._event.EventDispatcher.dispatch (kivy/_event.c:6970) 
    File "kivy/_event.pyx", line 1168, in kivy._event.EventObservers.dispatch (kivy/_event.c:12154) 
    File "kivy/_event.pyx", line 1092, in kivy._event.EventObservers._dispatch (kivy/_event.c:11729) 
    File "/home/onehitfinish/Downloads/Gregulator Files/test.py", line 81, in win_cb 
    MainScreen().font_size = new_size 
    File "/home/onehitfinish/Downloads/Gregulator Files/test.py", line 41, in __init__ 
    super(MainScreen, self).__init__(**kwargs) 
    File "/usr/lib/python3.4/site-packages/kivy/uix/relativelayout.py", line 255, in __init__ 
    super(RelativeLayout, self).__init__(**kw) 
    File "/usr/lib/python3.4/site-packages/kivy/uix/floatlayout.py", line 66, in __init__ 
    super(FloatLayout, self).__init__(**kwargs) 
    File "/usr/lib/python3.4/site-packages/kivy/uix/layout.py", line 66, in __init__ 
    super(Layout, self).__init__(**kwargs) 
    File "/usr/lib/python3.4/site-packages/kivy/uix/widget.py", line 271, in __init__ 
    Builder.apply(self) 
    File "/usr/lib/python3.4/site-packages/kivy/lang.py", line 1872, in apply 
    self._apply_rule(widget, rule, rule) 
    File "/usr/lib/python3.4/site-packages/kivy/lang.py", line 2018, in _apply_rule 
e), cause=tb) 
kivy.lang.BuilderException: Parser: File "main.kv", line 46: 
... 
     44:  text: "Simplify Fraction" 
     45:  pos_hint: {"right": 1, "top":0.2} 
>> 46:  font_size: root.font_size 
     47: 
     48: 
... 
BuilderException: Parser: File "main.kv", line 46: 
... 
     44:  text: "Simplify Fraction" 
     45:  pos_hint: {"right": 1, "top":0.2} 
>> 46:  font_size: root.font_size 
     47: 
     48: 
... 
AttributeError: 'MainScreen' object has no attribute 'font_size' 
    File "/usr/lib/python3.4/site-packages/kivy/lang.py", line 1649, in create_handler 
    return eval(value, idmap) 
    File "main.kv", line 46, in <module> 
    font_size: root.font_size 
    File "kivy/weakproxy.pyx", line 19, in  kivy.weakproxy.WeakProxy.__getattr__ (kivy/weakproxy.c:1101) 

    File "/usr/lib/python3.4/site-packages/kivy/lang.py", line 2011, in _apply_rule 
value, rule, rctx['ids']) 
    File "/usr/lib/python3.4/site-packages/kivy/lang.py", line 1654, in create_handler 
cause=tb) 

上解決這個，或者暗示這樣做的另一種方式，因爲我很新的Kivy將不勝感激任何幫助。

Answer 1

嘗試定義FONT_SIZE作爲NumericProperty在MainScreen：

from kivy.properties import NumericProperty 

class MainScreen(Screen): 

    font_size = NumericProperty() 

    def __init__(self, **kwargs): 
     super(MainScreen, self).__init__(**kwargs) 
     self.font_size = 25