Python| Kivy 中使用 .kv 文件的动画

Kivy 是Python中一个独立于平台的 GUI 工具。因为它可以在Android、IOS、Linux、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Desktops应用程序上使用。

动画片：

Animation 和 AnimationTransition 用于为 Widget 属性设置动画。您必须至少指定一个属性名称和目标值。要使用动画，请按照下列步骤操作：

设置一个动画对象
在 Widget 上使用 Animation 对象

To use animation you must have to import:
from kivy.animation import Animation

Basic Approaches: 

1) import runTouchApp
2) import Builder
3) import Widget
4) import Animation
5) import Clock
6) import Window
7) import random
8) import listproperty
9) Build the .kv file
10) Create root class
11) Create the clock and anim react class used to animate the boxes
12) Run the App

在下面的示例中，我们创建了两个框（红色和绿色），其中我们为红色框提供动画，即当应用程序启动时，红色框处于其动画视图中，但为了清除概念，我提供了绿色框点击时提供随机动画，即它随机地去任何地方。
该程序由两个主要类组成，首先是时钟类，它用于红色框，因为我们将其声明为动画，而绿色框动画在动画类中。

要提供运动，您必须使用速度。

方法的实施：

Python3

# work same as kivy.App used to run the App
from kivy.base import runTouchApp
 
# to use .kv file as a string we have to import it
from kivy.lang import Builder
 
# A Widget is the base building block of GUI interfaces in Kivy
from kivy.uix.widget import Widget
 
# The Clock object allows you to schedule a
# function call in the future
from kivy.clock import Clock
 
# Animation and AnimationTransition are
# used to animate Widget properties
from kivy.animation import Animation
 
# The Properties classes are used when
# you create an EventDispatcher.
from kivy.properties import ListProperty
 
# Core class for creating the default Kivy window.
from kivy.core.window import Window
 
# As name suggest used when random things required
from random import random
 
 
# load the kv file as string
Builder.load_string('''
:
 
# Setting the position (initial) of boxes
 
    ClockRect:
        pos: 300, 300
    AnimRect:
        pos: 500, 300
 
# creation and animation of red box
:
    canvas:
        Color:
            rgba: 1, 0, 0, 1
        Rectangle:
            pos: self.pos
            size: self.size
 
# creation and animation of red box
:
    canvas:
        Color:
            rgba: 0, 1, 0, 1
        Rectangle:
            pos: self.pos
            size: self.size
''')
 
 
# Create the root class
class Root(Widget):
    pass
 
 
# Create the clock class Then is when clicked
# how much time to animate
# the red colour block animation is created by it
class ClockRect(Widget):
    velocity = ListProperty([10, 15])
 
    def __init__(self, **kwargs):
        super(ClockRect, self).__init__(**kwargs)
        Clock.schedule_interval(self.update, 1 / 60.)
 
    def update(self, *args):
        self.x += self.velocity[0]
        self.y += self.velocity[1]
 
        if self.x < 0 or (self.x + self.width) > Window.width:
            self.velocity[0] *= -1
        if self.y < 0 or (self.y + self.height) > Window.height:
            self.velocity[1] *= -1
 
 
# Create the Animation class
# And add animation
# green colour box is animated through this class
class AnimRect(Widget):
     
    def anim_to_random_pos(self):
        Animation.cancel_all(self)
        random_x = random() * (Window.width - self.width)
        random_y = random() * (Window.height - self.height)
 
        anim = Animation(x = random_x, y = random_y,
                         duration = 4,
                         t ='out_elastic')
        anim.start(self)
 
    def on_touch_down(self, touch):
        if self.collide_point(*touch.pos):
            self.anim_to_random_pos()
 
# run the App
runTouchApp(Root())

输出：

动画输出视频：