在Kivy中旋转图像而不使用Builder/。kv文件和数字属性

Animation 旋转图像。

我想知道如何在不使用 .kv 文件(或 Builder.load_string

#! /usr/bin/env python3
import kivy
kivy.require('1.9.1')

from kivy.app import App
from kivy.uix.widget import Widget
from kivy.uix.label import Label
from kivy.uix.image import Image
from kivy.uix.floatlayout import FloatLayout
from kivy.graphics import Rectangle, Color, Rotate, PushMatrix, PopMatrix
from kivy.core.window import Window
from kivy.clock import Clock
from kivy.graphics.svg import Svg
from kivy.animation import Animation
from kivy.lang import Builder
from kivy.properties import NumericProperty

import random

WINDOW_WIDTH, WINDOW_HEIGHT = Window.size

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


class Sprite( Image ):
    angle = NumericProperty(0)

    def __init__( self, x=0, y=0, **kwargs ):
        super( Sprite, self ).__init__( **kwargs )

        self.size_hint = (None, None)  # tell the layout not to size me
        self.angle     = 0
        self.source    = 'alien.png'
        self.size      = self.texture.size 

        if ( x == 0 and y == 0 ):
            self.pos   = ( random.randrange(0,WINDOW_WIDTH) , random.randrange(0,WINDOW_HEIGHT) )
        else:
            self.pos   = ( x,y )

        self.animate() # start moving animation

    def animateComplete( self, *kargs ):
        Animation.cancel_all( self ) # is this needed?
        self.angle = 0
        self.animate()

    def animate( self ):
        self.anim = Animation( angle=360, duration=1 )
        self.anim.bind( on_complete=self.animateComplete )
        self.anim.repeat = True
        self.anim.start( self )


class FPSText( Label ):
    def __init__( self, **kwargs ):
        super( FPSText, self ).__init__( **kwargs )
        self.size_hint = (None, None)  # tell the layout not to size me
        self.pos_hint = { 'right':1, 'top':1 }

    def update( self, count ):
        self.text = "%d aliens / %3.1f FPS" % ( count, Clock.get_fps() ) 
        self.size = self.texture_size


class AlienGame( FloatLayout ):
    def __init__(self, **kwargs):
        super( AlienGame, self).__init__(**kwargs)
        self.aliens = []
        self.fps_text = FPSText()
        self.add_widget( self.fps_text )
        self.addAlien( WINDOW_WIDTH//2, WINDOW_HEIGHT//2 )

    def addAlien( self, x=0, y=0 ):
        new_alien = Sprite( x, y )
        self.aliens.append( new_alien )
        self.add_widget( new_alien )

    def update( self, dt ):
        self.fps_text.text = '--'
        self.fps_text.update( len( self.aliens ) )

    def on_touch_down( self, touch ):
        if ( touch.is_double_tap ):
            for i in range( 7 ):
                self.addAlien()
        else: #if ( touch.is_single_tap ):  (no single tap property)
            self.addAlien( touch.pos[0], touch.pos[1]  )

class RotApp( App ):
    def build( self ):
        game = AlienGame()
        Clock.schedule_interval(game.update, 1.0 / 60.0)
        return game


if ( __name__ == '__main__' ):    
    RotApp().run()

我试过这样的方法:

class Sprite( Image ):
    def __init__( self, x=0, y=0, **kwargs ):
        super( Sprite, self ).__init__( **kwargs )

        self.size_hint = (None, None)  # tell the layout not to size me
        self.source    = 'alien.png'
        self.size      = self.texture.size

        # define the rotation
        with self.canvas.before:
            PushMatrix()
            self.rot = Rotate()
            self.rot.angle  = 0
            self.rot.origin = self.center
            self.rot.axis = (0, 0, 1)
        with self.canvas.after:
            PopMatrix()

但没能拿到 self.rot.angle 动画 对象