[英]kivy screens. Do I have to initialize with super?
# Declare both screens
class MenuScreen(Screen):
pass
class SettingsScreen(Screen):
pass
From this SO question : 从这个SO问题 :
class WelcomeScreen(Screen):
def __init__(self, **kwargs):
super(Screen,self).__init__(**kwargs)
Under which circumstances is it necessary to initialize the screen with super
and why ? 在哪种情况下需要用super
初始化屏幕,为什么?
Short answer: 简短回答:
No you don't have to use super when defining a Screen. 不,您在定义屏幕时不必使用super。 Yes you do always have to __init__
with super (if you use __init__
). 是的,你总是必须__init__
与super(如果你使用__init__
)。
Longer answer: 更长的回答:
It's nothing unique to screens. 这对屏幕来说并不是唯一的。 In the docs example, you aren't calling __init__
and passing any parameters so no super
is necessary. 在docs示例中,您不是在调用__init__
并传递任何参数,因此不需要super
。 You don't need an __init__
call to define a Kivy Screen. 您不需要__init__
调用来定义Kivy屏幕。 From the SO question, if you're running __init__
you're passing **kwargs up the object hierarchy and also re-defining __init__
which would normally run the initialization of the parent class. 从SO问题来看,如果你正在运行__init__
你将** kwargs传递给对象层次结构并重新定义__init__
,这通常会运行父类的初始化。 super
is used to allow you to pass **kwargs and run the parent __init__
without an explicit call to the parent class, in this case, Screen
inherits from RelativeLayout
, which itself inherits from FloatLayout
; super
用于允许你传递** kwargs并运行父__init__
而不显式调用父类,在这种情况下, Screen
继承自RelativeLayout
,它本身继承自FloatLayout
; without a super call you're overriding the parent class. 如果没有超级电话,你就会覆盖父类。
You don't need to call __init__
unless you have some use for it. 除非你有一些用处,否则你不需要调用__init__
。 Here is a Screen
from one of my apps, with no __init__
call (layout is set in the .kv file): 这是我的一个应用程序的Screen
,没有__init__
调用(布局在.kv文件中设置):
class LoginScreen(Screen):
def login(self):
self.parent.current = 'ParameterScreen'
You will use __init__
if you want to set the layout, content, properties, etc. of a screen at the moment when you instantiate the class you have created without defining these things in the .kv file; 如果要在实例化已创建的类时设置屏幕的布局,内容,属性等,而不在.kv文件中定义这些内容,则将使用__init__
; to do that you will also need super as described above. 要做到这一点,你还需要超级如上所述。 It's good practice in kivy though to use the .kv file when you can. 虽然你可以使用.kv文件,但这是kivy的好习惯。
In this example, I want to be able to access BottomBar's parent with self.caller, which I pass in as a **kwargs when I create it, and have this be defined as soon as the bar is instantiated; 在这个例子中,我希望能够使用self.caller访问BottomBar的父级,我在创建它时将其作为** kwargs传入,并在条形图实例化后立即定义; so I need to define it in __init__
which requires a super call. 所以我需要在__init__
中定义它,这需要一个超级调用。
class BottomBar(ActionBar):
titletext = StringProperty('')
def __init__(self,**kwargs):
self.caller = kwargs.get('caller')
super(BottomBar,self).__init__(**kwargs)
def change_title(self,newtitle):
self.titletext = newtitle
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