Python| Kivy 中的相对布局

Kivy 是Python中一个独立于平台的 GUI 工具。因为它可以在Android、IOS、Linux和Windows等平台上运行。它基本上是用来开发Android应用程序的，但这并不意味着它不能在桌面应用程序上使用。

Kivy Tutorial – Learn Kivy with Examples. 

相对布局：

• 相对布局与 FloatLayout 类似，不同之处在于它的子小部件相对于布局定位。
• 此布局的操作方式与 FloatLayout 相同，但定位属性（x、y、center_x、right、y、center_y 和 top）是相对于布局大小而不是窗口大小的。
• 实际上，无论绝对定位还是相对定位，当布局位置发生变化时，小部件都会移动。
• 当 position=(0, 0) 的小部件被添加到RelativeLayout 时，现在如果RelativeLayout 的位置发生变化，子小部件也会移动。 Child 小部件坐标保持不变，即 (0, 0)，因为它们始终相对于父布局。
• 可用的 pos_hint 键（x、center_x、right、y、center_y 和 top）对于对齐边缘或居中很有用。
  例如：
  pos_hint: {'center_x':.5, 'center_y':.5} 将在中间对齐 Widget，无论窗口大小如何。

使用RelativeLayout 需要做的第一件事就是导入它。

from kivy.uix.relativelayout import RelativeLayout

笔记：
此布局允许您为孩子设置相对坐标。如果要绝对定位，请使用 FloatLayout。在 RelativeLayout 中，必须给出每个子窗口小部件的大小和位置。这也做了动态放置。

We can do relative positioning by:
pos_hint: provide hint of position
We can define upto 8 keys i.e. it takes arguments in form of dictionary.
pos_hint = {“x”:1, “y”:1, “left”:1, “right”:1, "center_x":1, "center_y":1,
           “top”:1, “bottom”:1("top":0)}

笔记：
Floatlayout 和 RelativeLayout 都支持绝对和相对定位，具体取决于使用的是pos_hint还是 pos。但是如果你想要绝对定位，使用 FloatLayout。

Basic Approach to create Relative Layout:

1) import kivy
2) import kivyApp
3) import button
4) import Relativelayout
5) Set minimum version(optional)
6) create App class:
        - define build() function
7) return Layout/widget/Class(according to requirement)
8) Run an instance of the class

使用 pos 实现方法：
它只是将位置分配给按钮。由于相对布局不依赖于窗口大小，它现在固定到该位置，如果您将窗口大小设置为小，它可能会消失而不是自行调整。

Python3

# Sample Python application demonstrating the
# working of RelativeLayout in Kivy
 
# import modules
import kivy
 
# base Class of your App inherits from the App class.
# app:always refers to the instance of your application
from kivy.app import App
 
# creates the button in kivy
# if not imported shows the error
from kivy.uix.button import Button
 
# This layout allows you to set relative coordinates for children.
from kivy.uix.relativelayout import RelativeLayout
 
# To change the kivy default settings
# we use this module config
from kivy.config import Config
     
# 0 being off 1 being on as in true / false
# you can use 0 or 1 && True or False
Config.set('graphics', 'resizable', True)
 
# creating the App class
class MyApp(App):
 
    def build(self):
 
        # creating Relativelayout
        Rl = RelativeLayout()
 
        # creating button
        # a button 30 % of the width and 20 %
        # of the height of the layout and
        # positioned at (x, y), you can do
        # The position does not depend on window size
        # it just positioned at the given places:
        btn = Button(text ='Hello world',
                 size_hint =(.2, .2),
                 pos =(396.0, 298.0))
        btn1 = Button(text ='Hello world !!!!!!!!!',
                 size_hint =(.2, .2),
                 pos =(-137.33, 298.0))
 
        # adding widget i.e button
        Rl.add_widget(btn)
        Rl.add_widget(btn1)
                 
        # return the layout
        return Rl
 
# run the App
if __name__ == "__main__":
    MyApp().run()

输出：

现在，如果您希望按钮根据窗口进行自我调整，则使用pos_hint 。

使用 pos_hint 的实现方法

Python3

# Sample Python application demonstrating the
# working of RelativeLayout in Kivy
 
# import modules
import kivy
 
# base Class of your App inherits from the App class.
# app:always refers to the instance of your application
from kivy.app import App
 
# creates the button in kivy
# if not imported shows the error
from kivy.uix.button import Button
 
# This layout allows you to set relative coordinates for children.
from kivy.uix.relativelayout import RelativeLayout
 
# To change the kivy default settings
# we use this module config
from kivy.config import Config
     
# 0 being off 1 being on as in true / false
# you can use 0 or 1 && True or False
Config.set('graphics', 'resizable', True)
 
# creating the App class
class Relative_Layout(App):
     
    def build(self):
 
        # creating Relativelayout
        rl = RelativeLayout()
       
        # creating button
        # size of button is 20 % by height and width of layout
        # position is bottom left i.e x = 0, y = 0
        b1 = Button(size_hint =(.2, .2),
                    pos_hint ={'x':0, 'y':0},
                    text ="B1")
         
        # position is bottom right i.e right = 1, y = 0
        b2 = Button(size_hint =(.2, .2),
                    pos_hint ={'right':1, 'y':0},
                    text ="B2")
 
        b3 = Button(size_hint =(.2, .2),
                    pos_hint ={'center_x':.5, 'center_y':.5},
                    text ="B3")
 
        b4 = Button(size_hint =(.2, .2),
                    pos_hint ={'x':0, 'top':1},
                    text ="B4")
 
        b5 = Button(size_hint =(.2, .2),
                    pos_hint ={'right':1, 'top':1},
                    text ="B5")
         
         
 
        # adding button to widget
        rl.add_widget(b1)
        rl.add_widget(b2)
        rl.add_widget(b3)
        rl.add_widget(b4)
        rl.add_widget(b5)
     
         
        # returning widget
        return rl
# run the App
if __name__  == "__main__":
    Relative_Layout().run()

输出：