Question

我正在尝试学习用于Python GUI编程的Kivy软件包的基础。我已经完成了Pong教程（https://www.facebook.com/ads/library/api/?source=archive-landing-page），并希望通过每次在击球时改变其颜色来测试我的理解能力。这是行不通的-每次球撞到墙时，我都会说一个错误，即没有Color属性。我在做什么错了？

main.py

from kivy.app import App
from kivy.uix.widget import Widget
from kivy.properties import  NumericProperty, ReferenceListProperty, ObjectProperty
from kivy.vector import Vector
from kivy.clock import Clock
from kivy.graphics import Color
from random import randint

class PongBall(Widget):
    vel_x = NumericProperty(0)
    vel_y = NumericProperty(0)
    vel = ReferenceListProperty(vel_x,vel_y)

    def move(self):
        self.pos = Vector(*self.vel) + self.pos

class PongGame(Widget):
    ball = ObjectProperty(None)

    def serve_ball(self):
        self.ball.center = self.center
        self.ball.vel = Vector(4,0).rotate(randint(0,360))

    def update(self, dt):
        self.ball.move()

        if(self.ball.y < 0) or (self.ball.top > self.height):
            self.ball.vel_y *= -1
            self.ball.Color(1,0,0)

        if(self.ball.x < 0) or (self.ball.right > self.width):
            self.ball.vel_x *= -1
            self.ball.Color(0,1,0)


class PongApp(App):
    def build(self):
        game = PongGame()
    game.serve_ball()
    Clock.schedule_interval(game.update, 1.0/60.0)
    return game


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

KV文件：

#:kivy 1.0.9

<PongBall>:
    size: 50, 50
    canvas:
        Ellipse:
            pos: self.pos
            size: self.size
        Color:
            rgba: 1, 1, 0, 0

<PongGame>:
    ball: pong_ball

    canvas:
        Rectangle:
            pos: self.center_x - 5, 0
            size: 10, self.height

    Label:
        font_size: 70
        center_x: root.width / 4
        top: root.top - 50
        text: "0"

    Label:
        font_size: 70
        center_x: root.width * 3 / 4
        top: root.top - 50
        text: "0"

    PongBall:
        id: pong_ball
        center: self.parent.center

Answer 1

您必须执行以下操作：

创建一个ListProperty来获取颜色信息，并在.kv中进行绑定。
颜色指令必须在椭圆指令之前：

class PongBall(Widget):
    vel_x = NumericProperty(0)
    vel_y = NumericProperty(0)
    vel = ReferenceListProperty(vel_x,vel_y)
    color = ListProperty((1, 1, 1, 1)) # <---

    def move(self):
        self.pos = Vector(*self.vel) + self.pos

class PongGame(Widget):
    ball = ObjectProperty(None)

    def serve_ball(self):
        self.ball.center = self.center
        self.ball.vel = Vector(4,0).rotate(randint(0,360))

    def update(self, dt):
        self.ball.move()

        if(self.ball.y < 0) or (self.ball.top > self.height):
            self.ball.vel_y *= -1
            self.ball.color = (1, 0, 0, 1) # <---

        if(self.ball.x < 0) or (self.ball.right > self.width):
            self.ball.vel_x *= -1
            self.ball.color = (0, 1, 0, 1) # <---
# ...

<PongBall>:
    size: 50, 50
    canvas:
        Color:
            rgba: self.color # <---
        Ellipse:
            pos: self.pos
            size: self.size
# ...

如何在Kivy中更改小部件颜色

1 个答案: