Kivy 简明教程
首先,有两个网址你不得不看:
- 在官网逛逛,顺便看看最下面的代码,try to run it.
- sentdex大神的入门级教程。
Kivy总体思想是:kv代码管界面,python代码管逻辑。
然后重点来了, 我主要讲三件事:(kv访问Python;Python访问kv;窗口)。
一阶段:
1.Python访问kv
Python可以直接调用kv代码。如:
from kivy.app import Appfrom kivy.lang import Builder kv = Builder.load_string(''' Button: text: "I was created by kv codes" ''') class TestApp(App): def build(self): return kv TestApp().run()
2.窗口
kv代码中被<>
包裹住的是某个class的名字,这个class需在python代码中声明,它们代表同一个class。
from kivy.app import Appfrom kivy.lang import Builder from kivy.uix.screenmanager import Screen Builder.load_string('''Label: text: "My mother screen was created by kv and python codes." ''') class OneScreen(Screen): pass class TestApp(App): def build(self): return OneScreen() TestApp().run()
3. kv访问Python
在.kv文件或kv代码里,root只代表其上层被<>包裹住的类。如:
from kivy.app import Appfrom kivy.lang import Builder from kivy.uix.screenmanager import Screen Builder.load_string('''Button: text: 'Click me' on_release: print(root.__class__) ''') class OneScreen(Screen): pass class TestApp(App): def build(self): return OneScreen() TestApp().run()
二阶段:
1. kv访问Python
from kivy.app import Appfrom kivy.lang import Builder from kivy.uix.screenmanager import Screen Builder.load_string('''BoxLayout: Button: text: 'Click me' on_release: root.do_something() Button: text: 'Who made this?' on_release: print(root.author) ''') class OneScreen(Screen): def __init__(self, **kwargs): self.author = 'yingshaoxo' super(OneScreen, self).__init__(**kwargs) def do_something(self): print('2333') class TestApp(App): def build(self): return OneScreen() TestApp().run()
2. Python访问kv
你需要给kv组件一个id,用以标明其唯一性。再使用ids方法调用它。如:
from kivy.app import Appfrom kivy.lang import Builder from kivy.uix.screenmanager import Screen Builder.load_string('''BoxLayout: Button: id: one_ask text: 'Who made this?' on_release: root.do_something() ''') class OneScreen(Screen): def __init__(self, **kwargs): self.author = 'yingshaoxo' super(OneScreen, self).__init__(**kwargs) def do_something(self): self.ids['one_ask'].text = self.author class TestApp(App): def build(self): return OneScreen() TestApp().run()
3. 窗口
As far as I see,在做程序的时候,你会遇到很多窗口。所以ScreenManager
这时候派上用场了。
from kivy.app import Appfrom kivy.lang import Builder from kivy.uix.screenmanager import ScreenManager Builder.load_string(''': Screen: name: 'home' Button: text: 'Go to another screen' on_release: root.current = 'another' Screen: name: 'another' Button: text: "Go back home" on_release: root.current = 'home' ''') class ScreenManager(ScreenManager): pass class TestApp(App): def build(self): return ScreenManager() TestApp().run()
三阶段:
1+2. 窗口、kv访问Python
In fact, 你可以把ScreenManager
看成一个很大的widget
。
但如果所有的数据操作(root.function
)都在一个 ScreenManager
class里做的话显然不科学。
所以我们最好把每个窗口都在Python里声明一个class,这样既可以有程序启动时的总操作,又可以有各个子窗口的分操作。看示例:
from kivy.app import Appfrom kivy.lang import Builder from kivy.uix.screenmanager import ScreenManager, Screen Builder.load_string(''': HomeScreen AnotherScreen : name: 'home' Button: text: 'Go to another screen' on_release: root.manager.current = 'another' : name: 'another' Button: text: "Go back home" on_release: root.manager.current = 'home' ''') class ScreenManager(ScreenManager): pass class HomeScreen(Screen): pass class AnotherScreen(Screen): pass class TestApp(App): def build(self): return ScreenManager() TestApp().run()
我们可以看到示例不光在kv代码中绑定了两个Screen
class,还引用了一个root.manager
。没错,那是从screen
class得到screenmanager
class的方法。
3. Python访问kv
直接用kv代码预先定义控件(如按钮)的行为有时不能满足我们的需求,于是我们可能需要临时改变按钮的行为:
from kivy.app import Appfrom kivy.lang import Builder from kivy.uix.screenmanager import Screen from time import gmtime, strftime # this equls cv codes #... Builder.load_string(""" #:import gmtime time.gmtime #:import strftime time.strftimeBoxLayout: orientation: 'vertical' Button: id: change_itself text: 'I can change myself' on_release: root.ids['change_itself'].text = strftime("%a, %d %b %Y %H:%M:%S", gmtime()) Button: id: change_all text: 'I can change our behavior' on_release: root.change_all() """) class RootWidget(Screen): def change_all(self): print(self.ids) for instance_class in self.ids.values(): instance_class.text = 'Exit' instance_class.bind(on_release=exit) class TestApp(App): def build(self): return RootWidget() if __name__ == '__main__': TestApp().run()
四阶段:
1. kv访问Python
from kivy.app import Appfrom kivy.lang import Builder from kivy.uix.screenmanager import Screen Builder.load_string('''Label: text: app.saying ''') class OneScreen(Screen): pass class TestApp(App): def __init__(self, **kwargs): self.saying = 'I was read from app instance.' super(OneScreen, self).__init__(**kwargs) def build(self): return OneScreen() TestApp().run()
五阶段:Show time!
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