kivy 的on_touch_move和on_touch_down

一个例子说明一切

import kivyfrom random import randomfrom kivy.app import Appfrom kivy.uix.widget import Widgetfrom kivy.uix.button import Buttonfrom kivy.graphics import Color, Ellipse, Lineclass Flowers_back(Widget):
    def _my_init(self):
        self.x_bef = 0.
        self.y_bef = 0.
        self.big = 30.
        self.c = random(), 1, 1
        self.is_start = True

    def __init__(self):
        super(Flowers_back, self).__init__()
        self._my_init()

    def on_touch_down(self, touch):
        self._my_init()
    def on_touch_move(self, touch):
        print('hello', touch)
        color = self.c        with self.canvas:
            d = self.big            if self.is_start:
                self.is_start = False
            else:
                Color(0, 0, 0, 0.2, mode='rgba')
                Ellipse(pos=(self.x_bef - d / 2, self.y_bef - d / 2), size=(d+5, d+5))
                Ellipse(pos=(self.x_bef - d / 2 + d, self.y_bef - d / 2 + d), size=(d / 2 +5, d / 2 + 5))

            Color(*color, mode='hsv')
            Ellipse(pos=(touch.x - d / 2, touch.y - d / 2), size=(d, d))
            Ellipse(pos=(touch.x - d / 2 + d, touch.y - d / 2 + d), size=(d/2, d/2))
            if self.big <= 80:
                self.big += 2.
            self.x_bef = touch.x
            self.y_bef = touch.yclass TestApp(App):

    def build(self):
        parent = Widget()
        self.painter = Flowers_back()
        clearbtn = Button(text='Clear')
        clearbtn.bind(on_release=self.clear_canvas)
        parent.add_widget(self.painter)
        parent.add_widget(clearbtn)
        return parent    def clear_canvas(self, obj):
        self.painter.canvas.clear()if __name__ == '__main__':
    TestApp().run()

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