Kivy跨平台开源框架

灰太狼 2022-02-23 12:50 702阅读 0赞

**简介：**  
Kivy 是一套用于跨平台快速应用开发的开源框架，只需要编写一套代码，就可运行于各大桌面及移动平台上（包括 Linux、Windows、OS X、Android、iOS、以及 Raspberry Pi）， Kivy 采用 Python 和 Cython 编写。

**在Windows系统中安装Kivy：**  
请确保已经安装了 Python3及最新的pip。  
一、安装 kivy（最新下载安装地址 [https://kivy.org/\#download）][https_kivy.org_download]

1.  输入 cmd，启动 Windows 命令行窗口
2.  pip 安装 kivy 依赖：在 windows 命令行中，执行以下命令

python -m pip install docutils pygments pypiwin32 kivy.deps.sdl2 kivy.deps.glew
    python -m pip install kivy.deps.gstreamer

1.  安装 kivy：在 windows 命令行中，执行以下命令

python -m pip install kivy

1.  安装 kivy 官方示例：在 windows 命令行中，执行以下命令

python -m pip install kivy_examples

二、验证 kivy  
在 IDLE 中输入下面代码

from kivy.app import App
    from kivy.uix.button import Button
    
    class TestApp(App):
        def build(self):
            return Button(text='iPaoMi')
            
    TestApp().run()

执行上面的代码，会运行如下：![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM4ODgyMzI3_size_16_color_FFFFFF_t_70_pic_center]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM4ODgyMzI3_size_16_color_FFFFFF_t_70_pic_center 1]  
最终通过 kivy 提供的打包工具，可以将 kivy 程序打包，运行到不同的平台上。

**Kivy官方文档：[https://kivy.org/doc/stable/][https_kivy.org_doc_stable]**  
**Kivy 简明教程：[https://www.kancloud.cn/gthank/kivydoc/127793][https_www.kancloud.cn_gthank_kivydoc_127793]**  
Kivy总体思想是：Kv代码管界面，Python代码管逻辑；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 App
    from 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的名称，这个class需在python代码中声明，它们代表同一个class。

from kivy.app import App
    from kivy.lang import Builder
    from kivy.uix.screenmanager import Screen
    
    Builder.load_string('''
    <OneScreen>
        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 App
    from kivy.lang import Builder
    from kivy.uix.screenmanager import Screen
    
    Builder.load_string('''
    <OneScreen>
        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 App
    from kivy.lang import Builder
    from kivy.uix.screenmanager import Screen
    
    Builder.load_string('''
    <OneScreen>
        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：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 App
    from kivy.lang import Builder
    from kivy.uix.screenmanager import Screen
    
    Builder.load_string('''
    <OneScreen>
        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：做程序的时候，会遇到很多窗口，这时ScreenManager就派上用场了。

from kivy.app import App
    from kivy.lang import Builder
    from kivy.uix.screenmanager import ScreenManager
    
    Builder.load_string('''
    <ScreenManager>:
        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：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。如：

from kivy.app import App
    from kivy.lang import Builder
    from kivy.uix.screenmanager import ScreenManager, Screen
    
    Builder.load_string('''
    <ScreenManager>:
        HomeScreen
        AnotherScreen
    
    <HomeScreen>:
        name: 'home'
        Button:
            text: 'Go to another screen'
            on_release: root.manager.current = 'another'
    
    <AnotherScreen>:
        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()

可以看到示例不光在kv代码中绑定了两个Screenclass，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需求，可能需要临时改变按钮的行为：

from kivy.app import App
    from 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.strftime
    
    <RootWidget>
        BoxLayout:
            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 App
    from kivy.lang import Builder
    from kivy.uix.screenmanager import Screen
    
    Builder.load_string('''
    <OneScreen>
        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()

[https_kivy.org_download]: https://kivy.org/#download%EF%BC%89
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM4ODgyMzI3_size_16_color_FFFFFF_t_70_pic_center]: /images/20220223/92204d0a3d084551968fe3151743ab7e.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM4ODgyMzI3_size_16_color_FFFFFF_t_70_pic_center 1]: /images/20220223/37f6e1b180754028bc0f2321f6595622.png
[https_kivy.org_doc_stable]: https://kivy.org/doc/stable/
[https_www.kancloud.cn_gthank_kivydoc_127793]: https://www.kancloud.cn/gthank/kivydoc/127793