Question

我正在尝试重构the last code sample，以便Button实际上是自己的on_release动作类。但是我的代码失败了。

我想不仅重构它（根据我下面的尝试），但我还需要将Button的文本设置为“清除”

from random import random
from kivy.app import App
from kivy.uix.widget import Widget
from kivy.uix.button import Button
from kivy.graphics import Color, Ellipse, Line


class MyPaintWidget(Widget):

    def on_touch_down(self, touch):
        userdata = touch.ud
        userdata['color'] = c = (random(), 1, 1)
        with self.canvas:
            Color(*c, mode='hsv')
            d = 30
            Ellipse(pos=(touch.x - d/2, touch.y - d/2), size=(d, d))
            userdata['line'] = Line(points=(touch.x, touch.y))

    def on_touch_move(self, touch):
        touch.ud['line'].points += [touch.x, touch.y]

class ClearButton(Button):
    def __init__(self, paint_widget):
        self.paint_widget=paint_widget

    def on_release(self, button):
        self.paint_widget.canvas.clear()

class MyPaintApp(App):

    def build(self):
        parent = Widget()
        painter = MyPaintWidget()
        clearbtn = ClearButton(painter)
        parent.add_widget(painter)
        parent.add_widget(clearbtn)

        return parent


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

Answer 1

没有子类化，你可以这样做：

class MyPaintWidget(Widget):
    # ... put your previous methods here
    def clear_canvas(self, *largs):
        self.canvas.clear()

class MyPaintApp(App):
    def build(self):
        root = FloatLayout()
        painter = MyPaintWidget()
        cleanbtn.bind(on_release=self.painter.clear_canvas)
        root.add_widget(painter)
        root.add_widget(clearbtn)
        return root

通过子类化，我更愿意使用Kv语言：

from kivy.lang import Builder

Builder.load_string('''
<ClearButton>:
    text: "Clear"
    on_release: app.painter.canvas.clear()
''')

class ClearButton(Button):
    pass

class MyPaintApp(App):
    def build(self):
        parent = Widget()
        painter = MyPaintWidget()
        clearbtn = ClearButton()
        parent.add_widget(painter)
        parent.add_widget(clearbtn)
        return parent

将on_release动作添加到kivy按钮

1 个答案: