Question

我正在尝试编写一个程序，以便沿着屏幕移动绘制汽车，并且向上和向下箭头键可以更改汽车的速度。但是，当我按下任一键时，都不会调用任何命令。我试过将bind_all和focus线更改为self.canvas，但这也不起作用。我该如何解决？

class racingCar:
    def __init__(self):
        window = Tk()
        window.title("Racing Car")

        self.cWidth = 500
        self.cHeight = 200
        self.canvas = Canvas(window, width = self.cWidth, height = self.cHeight, bg = "white")
        self.canvas.pack()

        self.x = 0
        self.y = self.cHeight
        self.drawCar(self.x, self.y)

        self.dx = 5
        self.sleepTime = 50
        self.animate()

        window.bind_all("<Up>", self.increaseSpeed)
        window.bind_all("<Down>", self.decreaseSpeed)
        window.focus()

        window.mainloop()

    def drawCar(self, x, y):
        self.canvas.create_rectangle(x, y - 20, x + 50, y - 10, fill = "yellow", tags = "car")
        self.canvas.create_oval(x + 10, y - 10, x + 20, y, fill = "black", tags = "car")
        self.canvas.create_oval(x + 30, y - 10, x + 40, y, fill = "black", tags = "car")
        self.canvas.create_polygon([x + 10, y - 20, x + 20, y - 30, x + 30, y - 30, x + 40, y - 20], fill = "blue", tags = "car")

    def increaseSpeed(self, event):
        print("pressed up")
        self.dx += 2.5

    def decreaseSpeed(self, event):
        print("pressed down")
        if self.dx > 0:
            self.dx -= 2.5

    def animate(self):
        while not self.dx == 0:
            self.canvas.move("car", self.dx, 0)
            self.canvas.after(self.sleepTime)
            self.canvas.update()
            if self.x < self.cWidth + 10:
                self.x += self.dx
            else:
                self.x = -60
                self.canvas.delete("car")
                self.drawCar(self.x, self.y)
racingCar()

Answer 1

请勿在运行tkinter的同一线程中使用while或sleep。

在这种情况下，after()的使用方式与sleep完全一样。

因为tkinter是单线程的，所以这些方法将阻塞主循环，直到循环结束或睡眠结束，其他任何事情都不会发生。更新画布的原因是因为您正在while循环中调用update，但是事件仍被阻止。

要解决此问题，请使用after()，因为它意味着tkinter中的这种循环。

我已将您的代码更新为使用after()，并对其进行了一些清理，以更严格地遵循PEP8样式指南。让我知道您是否有任何疑问。

import tkinter as tk


class RacingCar(tk.Tk):
    def __init__(self):
        super().__init__()
        self.title("Racing Car")

        self.c_width = 500
        self.c_height = 200
        self.canvas = tk.Canvas(self, width=self.c_width, height=self.c_height, bg="white")
        self.canvas.pack()

        self.x = 0
        self.y = self.c_height
        self.draw_car(self.x, self.y)

        self.dx = 5
        self.after_time = 50
        self.animate()

        self.bind("<Up>", self.increase_speed)
        self.bind("<Down>", self.decrease_speed)

    def draw_car(self, x, y):
        self.canvas.create_rectangle(x, y - 20, x + 50, y - 10, fill="yellow", tags="car")
        self.canvas.create_oval(x + 10, y - 10, x + 20, y, fill="black", tags="car")
        self.canvas.create_oval(x + 30, y - 10, x + 40, y, fill="black", tags="car")
        self.canvas.create_polygon([x + 10, y - 20, x + 20, y - 30, x + 30, y - 30, x + 40, y - 20],
                                   fill="blue", tags="car")

    def increase_speed(self, _):
        print("pressed up")
        self.dx += 2.5

    def decrease_speed(self, _):
        print("pressed down")
        if self.dx > 0:
            self.dx -= 2.5

    def animate(self):
        if self.dx != 0:
            self.canvas.move("car", self.dx, 0)
            if self.x < self.c_width + 10:
                self.x += self.dx
            else:
                self.x = -60
                self.canvas.delete("car")
                self.draw_car(self.x, self.y)
            self.after(self.after_time, self.animate)


RacingCar().mainloop()

Tkinter无法识别按键

1 个答案: