python - Tkinter - Canvas.move() 不会 move 列表中的最后一项

Question

我正在尝试使用 Tkinter 编写贪吃蛇游戏程序我的蛇由下面定义的圆列表组成。但是，当我调用 move 方法时，最后一个方法不会 move 。有什么问题吗？

    class Circle:

   def __init__(self,canv,x,y,index,direc):
        self._x = x
        self._y = y
        self._index = index
        self._direction = direc
        self._canvas = canv
        coordinat = (self._x)-5,(self._y)-5,(self._x)+5,(self._y)+5

        if index==0:
            color = "gold"
        else:
            color = "green"

        self._circle = canv.create_oval(coordinat ,fill=color, tags=str(self._index))

   def _move(self):
      if self._direction == "up":
         delta = (0,-5)
      elif self._direction == "down":
         delta = (0,5)
      elif self._direction == "left":
         delta = (-5,0)
      elif self._direction == "right":
         delta = (5,0)

      tag = str(self._index)
      self._canvas.move(tag, delta[0],delta[1])

我就是这么称呼她的

self._canvas = Canvas(self._playArea,width=750,height=450,bg="#1C1C1C")
    x = int(self._parent.winfo_width() / 4.)
    y = int(self._parent.winfo_height()/ 4.)
    circle = Circle(self._canvas,x,y,0,"right")
    self._circleList.append(circle)
    self._addCircle()
    self._addCircle()
    self._addCircle()
    self._addCircle()
    self._addCircle()

    self._canvas.place(x=0, y=0)

    for i in range(0,500):
       for x in self._circleList:
          x._move()
          root.update()
          root.after(10)

这是 addCircle 方法

length = len(self._circleList)
    if self._circleList[length-1]._direction == "right":
        x = (self._circleList[length-1]._x)-10
        y = self._circleList[length-1]._y
        d = "right"
    elif self._circleList[length-1]._direction == "left":
        x = (self._circleList[length-1]._x) + 10
        y = self._circleList[length-1]._y
        d = "left"
    elif self._circleList[length-1]._direction == "up":
        x = self._circleList[length-1]._x
        y = (self._circleList[length-1]._y)+10
        d = "up"
    elif self._circleList[length-1]._direction == "down":
        x = self._circleList[length-1]._x
        y = (self._circleList[length-1]._y)-10
        d = "down"

    newCircle = Circle(self._canvas,x,y,length,d)
    self._circleList.append(newCircle)

Answer 1

问题是您正在使用 index=0 创建第一个项目，然后使用 index作为识别该项目的标签。你不应该使用整数作为标签，它是为项目的 id 保留的，但是，你毕竟可以使用它。除此之外0被 Tcl 评估为 false，因此您没有有效地为其定义任何标签。事实证明，当您调用canvas.move(0, ...)时您不 move 任何创建的圆圈。但是您创建的下一个项目被分配了标签“1”，并且当您调用 canvas.move(1, ...) 时您实际上正在 move 之前创建的项目(具有“金色”颜色的项目)，因为 Tcl 自动为其分配了 id“1”。对创建的所有其他圈子重复此操作。

解决这个问题的快速方法是更改​​代码以使用 index + 1对于您正在通过的所有这些指数。但是您包含的代码中有几个问题，因此这里是一个修改后的代码，可以执行您所追求的操作:

import Tkinter

UP, RIGHT, DOWN, LEFT = range(4)

class Circle:
    def __init__(self, canv, x, y, direc, color):
        self.x, self.y = x, y
        self.direction = direc

        self._canvas = canv
        coord = (self.x)-5, (self.y)-5, (self.x)+5, (self.y)+5
        self._index = canv.create_oval(coord, fill=color)

    def move(self):
        y_sign = 1 if self.direction == DOWN else -1
        x_sign = 1 if self.direction == RIGHT else -1
        if self.direction in (UP, DOWN):
            delta = (0, y_sign * 5)
        else:
            delta = (x_sign * 5, 0)
        self._canvas.move(self._index, delta[0], delta[1])


def add_circle(canvas, l):
    d = l[-1].direction
    if d in (UP, DOWN):
        x = l[-1].x
        y = (1 if d == UP else -1) * 10 + l[-1].y
    else:
        x = (1 if d == LEFT else -1) * 10 + l[-1].x
        y = l[-1].y

    circle = Circle(canvas, x, y, d, "green")
    l.append(circle)


def move_circles(circle_l, root):
    for c in circle_l:
        c.move()
    root.after(50, lambda: move_circles(circle_l, root))

root = Tkinter.Tk()
width, height = 750, 450

canvas = Tkinter.Canvas(width=width, height=height, bg="#1C1C1C")
canvas.pack(fill=None, expand=False)

circle_l = []
circle = Circle(canvas, width / 4, height / 4, RIGHT, "gold")
circle_l.append(circle)
for _ in range(5):
    add_circle(canvas, circle_l)

move_circles(circle_l, root)

root.mainloop()