如何在Kivy中制作重复的旋转动画？
问题内容：
我想制作一个动画小部件，该小部件将旋转加载微调器图像。我看了Animation上课，看来它可以胜任。但是我找不到一种方法可以持续不断地沿单个方向旋转小部件
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()
启动它时，您会看到该小部件沿一个方向旋转360度，然后旋转。如何构建动画序列，以使角度每360度旋转一次不断增加或减小到0？
问题答案：
您可以在on_angle方法内部将角度设置为0 。这是一个稍作修改的版本：
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()
