如何在 Kivy 中制作重复的旋转动画?

2022-01-15 00:00:00 python kivy animation rotation

问题描述

我想制作一个可以旋转加载微调器图像的动画小部件.我查看了 Animation 类，它似乎可以完成这项工作.但是我找不到一种方法来不断地在一个方向上旋转小部件

I want to make an animated widget that would rotate the loading spinner image. I've looked into the Animation class and it seems like it can do the job. But I couldn't find a way to keep rotating the widget in a single direction constantly

这是我的代码:

from kivy.app import App
from kivy.lang import Builder
from kivy.uix.image import Image
from kivy.graphics import Rotate
from kivy.animation import Animation
from kivy.properties import NumericProperty

Builder.load_string('''                                                                                                                                        
<Loading>:                                                                                                                                                 
    canvas.before:                                                                                                                                             
        PushMatrix                                                                                                                                             
        Rotate:                                                                                                                                                
            angle: self.angle                                                                                                                                  
            axis: (0, 0, 1)                                                                                                                                    
            origin: self.center                                                                                                                                
    canvas.after:                                                                                                                                              
        PopMatrix                                                                                                                                              
''')

class Loading(Image):
    angle = NumericProperty(0)
    def __init__(self, **kwargs):
        super().__init__(**kwargs)
        anim = Animation(angle = 360)
        anim += Animation(angle = -360)
        anim.repeat = True
        anim.start(self)


class TestApp(App):
    def build(self):
        return Loading()

TestApp().run()

当您启动它时，您会看到该小部件在一个方向上旋转 360 度，然后旋转旋转.如何构建动画序列，使角度不断增加或每 360 次旋转下降到 0?

When you launch it, you'll see that the widget rotates 360 degrees in one direction and then turns the rotation around. How could I build the animation sequence so that the angle would constantly keep increasing or would be dropped to 0 every 360-rotation?

解决方案

您可以在 on_angle 方法中将角度设置为 0.这是一个稍作修改的版本:

You can set your angle to 0 inside on_angle method. Here's a slightly modified version:

from kivy.app import App
from kivy.lang import Builder
from kivy.uix.floatlayout import FloatLayout
from kivy.animation import Animation
from kivy.properties import NumericProperty

Builder.load_string('''                               
<Loading>:
    canvas.before:
        PushMatrix
        Rotate:
            angle: root.angle
            axis: 0, 0, 1
            origin: root.center
    canvas.after:
        PopMatrix


    Image:
        size_hint: None, None
        size: 100, 100
        pos_hint: {'center_x': 0.5, 'center_y': 0.5}
''')

class Loading(FloatLayout):
    angle = NumericProperty(0)
    def __init__(self, **kwargs):
        super(Loading, self).__init__(**kwargs)
        anim = Animation(angle = 360, duration=2) 
        anim += Animation(angle = 360, duration=2)
        anim.repeat = True
        anim.start(self)

    def on_angle(self, item, angle):
        if angle == 360:
            item.angle = 0


class TestApp(App):
    def build(self):
        return Loading()

TestApp().run()

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