弹跳球游戏 tkinter 画布

Question

I write a game in python in which the goal is to bounce the ball off the platform. Everything works pretty well, but the platform's movement is not that smooth. Could you help me make the platform movement more smooth? If the code isn't too clear, I'm sorry, but I'm new in python

import tkinter as tk
import random

root = tk.Tk()

width = 900
height = 500

canvas = tk.Canvas(root, bg='white', width=width, height=height)
canvas.pack()

x = random.randrange(700)

ball = canvas.create_oval(x+10, 10, x+50, 50, fill='green')

platform_y = height - 20
platform = canvas.create_rectangle(width//2-50, platform_y, width//2+50, platform_y+10, fill='black')

xspeed = 2
yspeed = 2
skore = 0
body = 0

def move_ball():
  global xspeed
  global yspeed
  x1, y1, x2, y2 = canvas.coords(ball)
  if x1 <= 0 or x2 >= width:
    xspeed = -xspeed
  if y1 <= 0:
    yspeed = 10
  elif y2 == platform_y: 
    cx = (x1 + x2) // 2
    px1, _, px2, _ = canvas.coords(platform)
    if px1 <= cx <= px2:
      yspeed = -10
    else:
      canvas.create_text(width//2, height//2, text='Game Over', font=('Arial Bold', 32), fill='red')
      return
  canvas.move(ball, xspeed, yspeed)
  canvas.after(20, move_ball)

def board_right(event):
  x1, y1, x2, y2 = canvas.coords(platform) 
  if x2 < width:
    dx = min(width-x2, 10)
    canvas.move(platform, dx, 0)

def board_left(event):
  x1, y1, x2, y2 = canvas.coords(platform)
  if x1 > 0:
    dx = min(x1, 10)
    canvas.move(platform, -dx, 0)

canvas.bind_all('<Right>', board_right)
canvas.bind_all('<Left>', board_left)

move_ball()

root.mainloop()

Answer 1

The problem is that the speed of the platform is dependent on the auto-repeat speed of your keyboard.

Instead of moving once for each <Right> or <Left> event, use a key press to start the platform moving in the desired direction and a key release to stop the platform moving. Then, use after to repeatedly move the platform in the given direction.

Example:

after_id = None
def platform_move(direction):
    """
    direction should be -1 to move left, +1 to move right,
    or 0 to stop moving
    """
    global after_id
    speed = 10
    if direction == 0:
        canvas.after_cancel(after_id)
        after_id = None
    else:
        canvas.move(platform, direction*speed, 0)
        after_id = canvas.after(5, platform_move, direction)

canvas.bind_all("<KeyPress-Right>", lambda event: platform_move(1))
canvas.bind_all("<KeyRelease-Right>", lambda event: platform_move(0))
canvas.bind_all("<KeyPress-Left>", lambda event: platform_move(-1))
canvas.bind_all("<KeyRelease-Left>", lambda event: platform_move(0))

The above code doesn't handle the case where you might press both keys at the same time, but that can be handled with a little additional logic. The point is to show how you can use the keys to start and stop an animation.