Kivy:如何将同时触摸限制在一个范围内？

from kivy.app import App
from kivy.uix.widget import Widget
from kivy.properties import NumericProperty
from kivy.uix.floatlayout import FloatLayout

class TouchWidget(Widget):
    touch_range = NumericProperty(100)  # 定义一个范围属性，默认为100

def on_touch_move(self, touch):
    if self.collide_point(*touch.pos):  # 判断触摸点是否在Widget内部
        x, y = touch.pos
        if x < self.x:
            x = self.x
        elif x > self.x + self.width:
            x = self.x + self.width
        if y < self.y:
            y = self.y
        elif y > self.y + self.height:
            y = self.y + self.height
        touch.pos = (x, y)  # 更新触摸点的位置

class MyLayout(FloatLayout):
    pass

class MyApp(App):
    def build(self):
        return MyLayout()

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