问题
I'm practicing Kivy with the PongGame code given in the tutorial. I want to know how to call a function - serve_ball2() in the class PongGame from a newly created class - PongSample. In the below code I created a class PongSample to serve the second ball once the first ball collide with the paddle.
Update : I can call the serve_ball2() from PongSample but the serve_ball2() doesn't function as intended i.e it doesn't serve the ball.
I've shared the complete code below. Thanks in advance
Pong.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, time
from threading import Thread
class PongPaddle(Widget):
score = NumericProperty(0)
def bounce_ball(self, ball):
if self.collide_widget(ball):
vx, vy = ball.velocity
offset = (ball.center_y - self.center_y) / (self.height / 2)
bounced = Vector(-1 * vx, vy)
vel = bounced * 1.1
ball.velocity = vel.x, vel.y + offset
PongSample().call_game()
class PongBall(Widget):
velocity_x = NumericProperty(0)
velocity_y = NumericProperty(0)
velocity = ReferenceListProperty(velocity_x, velocity_y)
def move(self):
self.pos = Vector(*self.velocity) + self.pos
class PongSample(Widget):
def call_game(self):
print 'PongSample'
ponggame=PongGame()
ponggame.serve_ball2()
class PongGame(Widget):
ball = ObjectProperty(None)
ball2 = ObjectProperty(None)
player1 = ObjectProperty(None)
player2 = ObjectProperty(None)
def serve_ball(self, vel=(4, 0)):
self.ball.center = self.center
self.ball.velocity = vel
def serve_ball2(self, vel=(3, 0)):
print 'Serve_ball2'
self.ball2.center = self.center
self.ball2.velocity = vel
def serve_down(self):
print 'Inside Serve Down'
self.ball.center = self.center
self.ball.velocity = Vector(4,0).rotate(-90)
def update(self, dt):
self.ball.move()
self.ball2.move()
#bounce of paddles
self.player1.bounce_ball(self.ball)
self.player2.bounce_ball(self.ball)
#bounce ball off bottom or top
if (self.ball.y < self.y) or (self.ball.top > self.top):
self.ball.velocity_y *= -1
if (self.ball2.y < self.y) or (self.ball2.top > self.top):
self.ball2.velocity_y *= -1
#went of to a side to score point?
if self.ball.x < self.x:
self.player2.score += 1
self.serve_ball(vel=(4, 0))
if self.ball.x > self.width:
self.player1.score += 1
self.serve_ball(vel=(-4, 0))
if self.ball2.x < self.x:
self.player2.score += 1
self.serve_ball2(vel=(3, 0))
if self.ball2.x > self.width:
self.player1.score += 1
self.serve_ball2(vel=(-3, 0))
def on_touch_move(self, touch):
if touch.x < self.width / 3:
self.player1.center_y = touch.y
if touch.x > self.width - self.width / 3:
self.player2.center_y = touch.y
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()
pong.kv:
#:kivy 1.8.0
<PongBall>:
size: 50, 50
canvas:
Ellipse:
pos: self.pos
size: self.size
<PongPaddle>:
size: 25, 200
canvas:
Rectangle:
pos:self.pos
size:self.size
<PongGame>:
ball: pong_ball
ball2: pong_ball2
player1: player_left
player2: player_right
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: str(root.player1.score)
Label:
font_size: 70
center_x: root.width * 3 / 4
top: root.top - 50
text: str(root.player2.score)
PongBall:
id: pong_ball
center: self.parent.center
PongBall:
id: pong_ball2
center: self.parent.center
PongPaddle:
id: player_left
x: root.x
center_y: root.center_y
PongPaddle:
id: player_right
x: root.width-self.width
center_y: root.center_y
回答1:
To use your class add game.serve_ball2() to PongApp
class PongApp(App):
def build(self):
game = PongGame()
game.serve_ball()
game.serve_ball2()
Clock.schedule_interval(game.update, 1.0 / 60.0)
return game
And add self.ball2 to bounce off the paddles:
#bounce of paddles
self.player1.bounce_ball(self.ball)
self.player2.bounce_ball(self.ball)
self.player1.bounce_ball(self.ball2)
self.player2.bounce_ball(self.ball2)
回答2:
I emphasize that this seems unnecessary, and that PongSample itself seems like it needn't exist at all. However, to do what you asked, I believe the following should work. One thing I really don't like about this however, is that a PongSample instance is created in the kv file, without any other purpose than to serve ball2. However...
Why not define the serve_ball2 function in the PongSample class instead, and pass ball2 to it?
Example:
class PongSample(Widget):
def serve_ball2(self, ball2, vel=(3,0)):
print 'Serve ball 2'
ball2.center = self.center
ball2.velocity = vel
And in the PongGame class:
class PongGame(Widget):
ball = ObjectProperty(None)
ball2 = ObjectProperty(None)
player1 = ObjectProperty(None)
player2 = ObjectProperty(None)
# add this
sample = ObjectProperty(None)
Then in the kv file:
# add at the top
<PongSample>:
size: self.size
pos: self.pos
# add the below in appropriate places within the PongGame definition
PongGame:
sample: pong_sample
PongSample:
id: pong_sample # now it's linked to 'sample' in PongGame
So now in PongGame you can call self.sample.serve_ball2(ball2) from any method.
来源：https://stackoverflow.com/questions/24424962/how-to-call-a-function-from-a-class-from-another-class-in-kivy-pong-ball-game