Python Turtle：开始倒计时卡住

Question

我正在制作一个躲避游戏，其中乌龟（形状像乌龟）必须避开其他乌龟（形状像鳄鱼）。我让游戏正常运行，但我试图在游戏开始前添加一个倒计时，该倒计时是 3,2,1,GO！

我的想法是，由于我拥有的 countdown_number 变量是 3、2、1，然后是 GO！，我可以通过让其他一切都依赖于 countdown_number 的值来让它在游戏的其余部分之前出现“去！”。

但是，现在，当我启动程序时，它卡在 3 上，并且在更新间隔重新开始后，而不是继续执行 2、1 和 GO！所以游戏无法开始。

我在 Stack Overflow 上看到了很多与运行计时器和游戏并发的事情有关的问题，但我需要在游戏开始之前发生这些问题。

import turtle
import random
import pygame

window_height = 600
window_width = 600

update_interval = 25

countdown_number = 3

river_width = 400
minimum_river_width = 200

border_height = 600

river_width_update = 0.5

safe_distance_from_border = border_height / 2 + 3

number_of_enemies = 10
enemies = []
enemy_speeds = []
enemy_width = 100
enemy_height = 40
enemy_speed_min, enemy_speed_max = 10, 20

safe_distance_from_enemy = 15

def startgame():
    global countdown_number
    if countdown_number >= 1:
        turtle.home()
        turtle.left(270)
        turtle.clear()
        turtle.speed(0)
        for _ in range(0,100,5):
            turtle.forward(1)
            turtle.color("grey"+str(_))
            turtle.write(countdown_number, align="center", font=("Arial", 200, "normal"))
    if countdown_number == 0:
        countdown_number = "GO!"
        turtle.home()
        turtle.left(270)
        turtle.clear()
        turtle.speed(0)
        for _ in range(0,100,5):
            turtle.forward(1)
            turtle.color("grey"+str(_))
            turtle.write(countdown_number, align="center", font=("Arial", 200, "normal"))
        turtle.clear()

    #print(number)

def gameover(msg):
    print(msg) # Probably comment this out later
    turtle.home()
    turtle.write(msg, align="center", font=("Arial", 24, "normal"))

def moveplayerturtle(x, y):
    if x > -window_width / 2 and x < window_width / 2:
        turtle.goto(x, y)

def updatescreen():

    global river_width
    global countdown_number
    if countdown_number != "GO!":
        startgame()

    if countdown_number == "GO!":

        if upper_river_border.ycor() >= window_height-200:
            upper_river_border.sety(upper_river_border.ycor() - river_width_update)

        if lower_river_border.ycor() <= -window_height+200:
            lower_river_border.sety(lower_river_border.ycor() + river_width_update)

        if upper_river_border.ycor() - turtle.ycor() < safe_distance_from_border:

            gameover("Game over!")

            return
        if turtle.ycor() - lower_river_border.ycor() < safe_distance_from_border:

            gameover("Game over!")

            return

        for i in range(number_of_enemies):

            enemies[i].forward(enemy_speeds[i])

            if enemies[i].xcor() > (window_width+enemy_width)/2:
                x = -(window_width+enemy_width)/2
                y = int(turtle.ycor())
                enemies[i].goto(x, y)
                s=1
                enemy_speeds[i]=int(random.randrange(10+s, 20+s))

            if turtle.distance(enemies[i]) < safe_distance_from_enemy:
                gameover("You lose!")
                return

    turtle.ontimer(updatescreen, update_interval)
    turtle.update()

turtle.setup(window_width, window_height) # Set the window size
turtle.bgcolor("DarkBlue")

turtle.tracer(False)

upper_river_border = turtle.Turtle()
upper_river_border.up()
lower_river_border = turtle.Turtle()
lower_river_border.up()

upper_river_border.shape("square")
lower_river_border.shape("square")

upper_river_border.color("DarkOrange4")
lower_river_border.color("DarkOrange4")

upper_river_border.shapesize(30, 40)
lower_river_border.shapesize(30, 40)

upper_river_border.sety((border_height + river_width) / 2)
lower_river_border.sety(-(border_height + river_width) / 2)

turtle.addshape("crocodile.gif")

for _ in range(number_of_enemies):

    enemy = turtle.Turtle()

    turtle.addshape("crocodile.gif")
    enemy.shape("crocodile.gif")
    enemy.up()
    x = -(window_width + enemy_width) / 2
    y = random.randint(-(river_width-enemy_height)/2, (river_width-enemy_height)/2)
    enemy.goto(x, y)

    enemies.append(enemy)

    enemy_speeds.append(random.randint(enemy_speed_min, enemy_speed_max))

turtle.shape("turtle")
turtle.left(180)
turtle.color("GreenYellow")
turtle.up()

turtle.ondrag(moveplayerturtle)

turtle.ontimer(updatescreen, update_interval)

turtle.done()

当我将倒计时作为自己的程序编写时，我已经让倒计时完全正常工作，所以我认为它必须与从倒计时序列过渡到导致问题的游戏循环本身有关.

任何帮助将不胜感激。

Answer 1

在启动屏幕倒计时时，您的线路已经交叉 - 在错误的时间调用了错误的东西。以下是我对最小修复的建议。首先，重新定义startgame()如下：

def startgame():
    global countdown_number

    turtle.home()
    turtle.clear()
    turtle.left(270)

    if countdown_number > 0:
        for grey in range(0, 100, 5):
            turtle.forward(1)
            turtle.color("grey" + str(grey))
            turtle.write(countdown_number, align="center", font=("Arial", 200, "normal"))

        countdown_number -= 1

        turtle.ontimer(startgame, countdown_interval)

    else:
        for grey in range(0, 100, 5):
            turtle.forward(1)
            turtle.color("grey" + str(grey))
            turtle.write("GO!", align="center", font=("Arial", 200, "normal"))

        turtle.clear()

        turtle.ontimer(updatescreen, countdown_interval)

接下来进行一些小的更改以适应此重写。在代码的顶部，添加定义：

countdown_interval = 1000

接近update_interval的定义。

在代码的底部，而不是：

turtle.ontimer(updatescreen, update_interval)

turtle.done()

这样做：

turtle.ontimer(startgame, update_interval)

turtle.done()

最后，在updatescreen() 中删除所有处理countdown_number 的代码：

global countdown_number
if countdown_number != "GO!":
    startgame()

if countdown_number == "GO!":

并根据需要重新缩进此函数的主体。

应该这样做。快乐躲避！