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。我已经研究过Animation班，看起来它可以完成这项工作。但我无法找到一个方法来保持在一个方向上旋转部件不断

这是我的代码有：

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() 

当你启动它，你会看到小部件旋转360单向旋转，然后转动旋转。我如何构建动画序列，以便角度会不断保持增长，或者每360次旋转将会降至0？

Answer 1

您可以在on_angle方法中将角度设置为0。这里有一个稍微修改的版本：

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()