如何根据Widget Kivy属性更新动态添加的**Ellipse(不使用Builder)的颜色？

Question

这与另一个问题非常相关.唯一的区别是我是动态添加Ellipse with self.canvas而不是使用Builder(Builder.load_string或Builder.load_file).因此,这里的代码,做工作.当您单击椭圆时,它会移动并更改颜色:

from kivy.app import App
from kivy.lang import Builder
from kivy.uix.widget import Widget
from kivy.properties import NumericProperty
from kivy.graphics import Color, Ellipse

Builder.load_string("""
<CircleWidget>:
    canvas:
        Color:
            rgba: self.r,1,1,1
        Ellipse:
            pos: self.pos
            size: self.size
""")

class CircleWidget(Widget):
    r = NumericProperty(0)
    def __init__(s, **kwargs):
        s.size= [50,50]
        s.pos = [100,50]
        super(CircleWidget, s).__init__(**kwargs)

    def on_touch_down(s, touch):
        if s.collide_point(touch.x,touch.y):    
            s.pos = [s.pos[1],s.pos[0]]     # this works
            s.r = 1.0                       # this also works

class TestApp(App):
    def build(s):
        parent = Widget()
        parent.add_widget(CircleWidget())
        return parent

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

如果我尝试不使用Builder它而做同样的事情,它就不再起作用了:

from kivy.app import App
from kivy.lang import Builder
from kivy.uix.widget import Widget
from kivy.properties import NumericProperty
from kivy.graphics import Color, Ellipse

class CircleWidget(Widget):
    r = NumericProperty(0)
    def __init__(s, **kwargs):
        s.size= [50,50]
        s.pos = [100,50]
        super(CircleWidget, s).__init__(**kwargs)
        with s.canvas:
            Color(s.r,1,1,1)
            Ellipse(pos = s.pos, size = s.size)

    def on_touch_down(s, touch):
        if s.collide_point(touch.x,touch.y):    
            s.pos = [s.pos[1],s.pos[0]]     # This doesn't work anymore
            s.r = 1.0                       # Neither do this

class TestApp(App):
    def build(s):
        parent = Widget()
        parent.add_widget(CircleWidget())
        return parent

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

代码运行,实际调用事件.更重要的是,Widget被移动(即使它在视觉上不清楚),但画布的说明没有更新.

有任何想法吗？

Answer 1

第一个版本有效,因为kv lang自动将画布重新绑定到表达式中的属性,因此这些行:

    Color:
        rgba: self.r,1,1,1

做的不仅仅是这个:

    Color(s.r,1,1,1)

你能做什么,howether,是绑定self.r自动重建你的画布说明.

在 __init__

self.bind(r=self.redraw)
self.bind(pos=self.redraw)
self.bind(size=self.redraw)

并移动

    with s.canvas:
        Color(s.r,1,1,1)
        Ellipse(pos = s.pos, size = s.size)

部分为一个名为的方法redraw,之前使用self.canvas.clear()调用.

完整结果:

from kivy.app import App
from kivy.uix.widget import Widget

from kivy.properties import NumericProperty
from kivy.graphics import Color, Ellipse

class CircleWidget(Widget):
    r = NumericProperty(0)

    def __init__(s, **kwargs):
        super(CircleWidget, s).__init__(**kwargs)
        s.bind(r=s.redraw)
        s.bind(pos=s.redraw)
        s.bind(size=s.redraw)
        s.size = [50, 50]
        s.pos = [100, 50]

    def redraw(s, *args):
        s.canvas.clear()
        with s.canvas:
            Color(s.r, 1, 1, 1)
            Ellipse(pos = s.pos, size = s.size)

    def on_touch_down(s, touch):
        if s.collide_point(touch.x, touch.y):
            print "gotcha"
            s.pos = [s.pos[1], s.pos[0]]
            s.r = 1.0

class TestApp(App):
    def build(s):
        parent = Widget()
        parent.add_widget(CircleWidget())
        return parent

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