这里显示了一种使用tkinterafter方法更新对象和关联的画布oval对象的位置的方法。它使用生成器函数沿圆形路径计算坐标，该圆形路径表示Celestial实例之一（名为planet_obj1）的轨道。
import math
try:
import tkinter as tk
except ImportError:
import Tkinter as tk # Python 2
DELAY = 100
CIRCULAR_PATH_INCR = 10
sin = lambda degs: math.sin(math.radians(degs))
cos = lambda degs: math.cos(math.radians(degs))
class Celestial(object):
# Constants
COS_0, COS_180 = cos(0), cos(180)
SIN_90, SIN_270 = sin(90), sin(270)
def __init__(self, x, y, radius):
self.x, self.y = x, y
self.radius = radius
def bounds(self):
""" Return coords of rectangle surrounding circlular object. """
return (self.x + self.radius*self.COS_0, self.y + self.radius*self.SIN_270,
self.x + self.radius*self.COS_180, self.y + self.radius*self.SIN_90)
def circular_path(x, y, radius, delta_ang, start_ang=0):
""" Endlessly generate coords of a circular path every delta angle degrees. """
ang = start_ang % 360
while True:
yield x + radius*cos(ang), y + radius*sin(ang)
ang = (ang+delta_ang) % 360
def update_position(canvas, id, celestial_obj, path_iter):
celestial_obj.x, celestial_obj.y = next(path_iter) # iterate path and set new position
# update the position of the corresponding canvas obj
x0, y0, x1, y1 = canvas.coords(id) # coordinates of canvas oval object
oldx, oldy = (x0+x1) // 2, (y0+y1) // 2 # current center point
dx, dy = celestial_obj.x - oldx, celestial_obj.y - oldy # amount of movement
canvas.move(id, dx, dy) # move canvas oval object that much
# repeat after delay
canvas.after(DELAY, update_position, canvas, id, celestial_obj, path_iter)
top = tk.Tk()
top.title('Circular Path')
canvas = tk.Canvas(top, bg='black', height=500, width=500)
canvas.pack()
sol_obj = Celestial(250, 250, 25)
planet_obj1 = Celestial(250+100, 250, 15)
sol = canvas.create_oval(sol_obj.bounds(), fill='yellow', width=0)
planet1 = canvas.create_oval(planet_obj1.bounds(), fill='blue', width=0)
orbital_radius = math.hypot(sol_obj.x - planet_obj1.x, sol_obj.y - planet_obj1.y)
path_iter = circular_path(sol_obj.x, sol_obj.y, orbital_radius, CIRCULAR_PATH_INCR)
next(path_iter) # prime generator
top.after(DELAY, update_position, canvas, planet1, planet_obj1, path_iter)
top.mainloop()
这是运行的样子：
602392714
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