python - 如何在 Kivy 中制作重复的旋转动画？

Question

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

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，您会看到小部件在一个方向上旋转 360 度，然后旋转一圈。我如何构建动画序列，使角度不断增加或每 360 度旋转一次下降到 0？

Answer 1

您可以在 on_angle 方法中将角度设置为 0。这是一个稍微修改过的版本:

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()