tkinter类内如何绑定Canvas对象 实现方向键控制飞船移动

存在的问题 #

• 拼写错误：down方法中self.spacehipx拼写错误，少了字母s，应为self.spaceshipx，导致速度变量赋值失效
• 缺少飞船移动的循环逻辑：仅在类初始化时执行了一次飞船移动方法，没有把飞船位置更新加入到和小行星同步的帧循环（move_active方法）中，即使修改了速度变量也不会触发位置刷新
• 按键绑定逻辑冗余：run方法中绑定按键时不需要引用全局实例SpaceF，直接绑定类内部的self.down方法即可，避免依赖全局变量
• 坐标方向逻辑错误：tkinter的Canvas坐标系左上角为原点(0,0)，y轴向下数值递增，原代码给y轴设的-10实际是向上移动，要实现向下移动应该设为正值

修复后的完整代码 #

from tkinter import *
from random import randint as rnd

class SpaceField:
    def __init__(self, window = None):
        self.window = window
        self.window = Tk()
        self.window.title("Asteriods")
        # Define canvas size and active flag
        self.wide, self.high, self.active = 700, 600, True
        self.spaceshipx, self.spaceshipy = 0, 0 # 初始化飞船速度为0
        self.canvas_display()
        self.asteriod_creation_seperation()
        self.spaceship_creation()
        #self.bullet_creation()

    def spaceship_creation(self):
        self.shipcoords = [] 
        self.spaceship = self.canvas.create_polygon(340,300,360,
            300, 350,280, outline ="white")
        self.shipcoords.append(self.spaceship)

    def spaceship_movement(self):
        # 按照当前速度更新飞船位置
        self.canvas.move(self.spaceship, self.spaceshipx, self.spaceshipy)

    def down(self, event):
        print(event.keysym)
        self.spaceshipx = 0
        self.spaceshipy = 10 # y轴正方向为向下，改为正值实现下移

    def asteriod_creation_seperation(self):
        self.asteroids, self.speed = [], []
        size, radius = 50, 25
        for i in range(25):
            spacex = rnd(size, self.wide - size)
            spacey = rnd(size, self.high - size)
            self.asteroids.append(
                self.canvas.create_oval(
                    spacex, spacey, spacex+size, spacey+size,
                    width=2, tags = "asteriod", outline = "white"))
            self.speed.append((rnd(1,4),rnd(1,4)))

    def asteriod_update(self):
        for i, a in enumerate(self.asteroids):
            xx, yy = self.speed[i]
            x, y, w, h = self.canvas.coords(a)
            if x < 0 or w > self.wide:
                xx = -xx * rnd(1, 4)
            if y < 0 or h > self.high:
                yy = -yy * rnd(1, 4)

            self.speed[i] = (max( -4, min( xx, 4)), max( -4, min( yy, 4 )))
            self.canvas.move(a, xx, yy)

    def move_active(self):
        if self.active:
            self.asteriod_update()
            self.spaceship_movement() # 每一帧同步更新飞船位置
            self.window.after(40, self.move_active)

    def canvas_display(self):
        self.canvas = Canvas(
            self.window, width = self.wide,
            height = self.high, background = "black")
        self.canvas.pack(expand = True, fill = "both")

    def run(self):
        self.window.bind("<KeyPress-Down>", self.down) # 简化绑定逻辑
        self.window.after(200, self.move_active)
        self.window.mainloop()


if __name__ == "__main__":
    SpaceF = SpaceField()
    SpaceF.run()

内容的提问来源于stack exchange，提问作者user14232195