Lisa Hasler Waters wrote:
> My students and I are creating a maze game in tkinter. We are trying to
> make the ball disappear when it hits the wall (black lines). We are not
> having much luck. The following code has run the best, but still, the ball
> does not disappear. Any advice would be appreciated!
You need to consider not just the ball, but the whole trajectory. When you
can only move up/down/left/right that is roughly the rectangle spread by the
starting and the end position of the ball.
I calculate that rectangle as (x0,y0)-(x1,y1) in the checked_move() method
below. I recommend that you use pen and paper, draw two rectangular "balls"
on a horizontal or vertical line and the rectangle between them to try it
yourself before you take a look.
I then use that rectangle to find overlapping canvas items. Of course the
ball will always overlap with itself, so I have to make sure to rule that
out.
While dabbling with the code I have also cleaned it up a bit -- but you
should still recognize it ;)
from tkinter import *
import random
import time
class Ball:
def __init__(self, canvas, color):
self.canvas = canvas
self.id = canvas.create_oval(
15, 15, 30, 30,
fill='Blue')
def checked_move(self, dx, dy):
"""Move unless we would hit a wall"""
x0, y0, x1, y1 = self.canvas.coords(self.id)
if dx > 0:
x1 += dx
else:
x0 += dx
if dy > 0:
y1 += dy
else:
y0 += dy
for id in self.canvas.find_overlapping(x0, y0, x1, y1):
if id != self.id:
# we will hit something other than ourselves
# jump back to the start instead of
# deleting ourselves
self.canvas.coords(self.id, 15, 15, 30, 30)
# uncomment line below if you insist on deletion
# self.canvas.delete(self.id)
return
self.canvas.move(self.id, dx, dy)
def mt(event):
STEP = 15
if event.keysym == 'Left':
ball.checked_move(-STEP, 0)
elif event.keysym == 'Up':
ball.checked_move(0, -STEP)
elif event.keysym == 'Down':
ball.checked_move(0, STEP)
elif event.keysym == 'Right':
ball.checked_move(STEP, 0)
WALLS = [
(0, 0, 0, 300, 20),
(0, 300, 300, 300, 10),
(80, 240, 80, 0, 10),
(160, 300, 160, 60, 10),
(240, 240, 240, 0, 10),
(300, 300, 300, 150, 10),
(300, 150, 600, 150, 10),
(80, 0, 2000, 0, 30),
(300, 75, 600, 75, 10),
(760, 0, 760, 300, 10),
(600, 75, 680, 75, 10),
]
def main():
global ball # needed for mt()
tk = Tk()
tk.title("Game")
tk.resizable(0, 0)
tk.wm_attributes("-topmost", 1)
canvas = Canvas(tk, width=1400, height=835, bd=0, highlightthickness=0)
canvas.pack()
ball = Ball(canvas, 'blue')
canvas.bind_all('<KeyPress-Up>', mt)
canvas.bind_all('<KeyPress-Down>', mt)
canvas.bind_all('<KeyPress-Left>', mt)
canvas.bind_all('<KeyPress-Right>', mt)
for wall in WALLS:
coords = wall[:4]
width = wall[4]
canvas.create_line(*coords, width=width, tags="wall")
tk.mainloop()
if __name__ == "__main__":
main()
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