Kivy：坐标

Question

在下面的代码中，我没有解释两个问题：

1. 如果我使用方法__init__ - ＆gt; Scene.canvas =无
2. 我不会对图像中的相对位置对象感兴趣。

我想从Kivy手册获得有关坐标系统的知识，但没有成功。

from kivy.app import App
from kivy.uix.widget import Widget
from kivy.core.window import Window
from kivy.lang import Builder
from kivy.uix.image import Image    
from kivy.graphics import Ellipse

class Scene(Widget):
    """
    def __init__(self):
        self.x = 0
        self.y = 100
        self.dir = 1
    """
    def set_par(self):
        self.x = 0
        self.y = 100
        self.dir = 1

    def create_ball(self):
        with self.canvas:
            Ellipse(pos = (0,0), size = (40, 40))
        img = Image(pos = (0,0), source = 'image1.png') # square 40x40pixels  
        self.add_widget(img)          

class SceneApp(App):
    def build(self):
        scene = Scene()
        scene.create_ball()

        return scene

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

Printscreen形成我的代码：

Answer 1

您未在super()方法中致电__init__。因此，Widget __init__方法会被彻底改写 然后使用FloatLayout代替Widget
你可以做这样的事情：

from kivy.app import App
from kivy.core.window import Window
from kivy.lang import Builder
from kivy.uix.image import Image
from kivy.uix.floatlayout import FloatLayout
from kivy.graphics import Ellipse

Window.size = (300, 300)

class Scene(FloatLayout):

    def __init__(self, **kwargs):
        super(Scene,self).__init__(**kwargs)
        self.size = 300,300

    def create_ball(self):
        img = Image(pos = (-130, -130), source = 'image1.png') # square 40x40pixels
        self.add_widget(img)
        with self.canvas:
            Ellipse(pos = (0,0), size = (40, 40))

class SceneApp(App):
    def build(self):
        scene = Scene()
        scene.create_ball()
        return scene

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