Python

Question

我正在使用 tkinter 制作程序。我有一个 canvas 和 canvas 里面的一只乌龟。目前，乌龟使用箭头键在屏幕上移动，但我希望它不能离开 canvas 的边界。这是我当前的代码

canvas = Tk.Canvas(master=self, width=300, height=300)
canvas.grid(row=2, column=2, columnspan=3, padx=50)

canvas.focus_set()

t = turtle.RawTurtle(canvas)
t.setheading(90)

left_bound = -(canvas.winfo_width() / 2)
right_bound = canvas.winfo_width() / 2
top_bound = canvas.winfo_height() / 2
bottom_bound = -(canvas.winfo_height() / 2)

tx = t.xcor()
ty = t.ycor()

if tx > right_bound or tx < left_bound:
    t.undo()
if ty > top_bound or ty < bottom_bound:
    t.undo()

def move_forward_keys(_):
   t.forward(10)

def move_left_keys(_):
   t.left(20)

def move_right_keys(_):
   t.right(20)

def move_back_keys(_):
   t.back(10)

canvas.bind("<Up>", move_forward_keys)
canvas.bind("<Left>", move_left_keys)
canvas.bind("<Right>", move_right_keys)
canvas.bind("<Down>", move_back_keys)

可能是因为我做错了什么，但这是我目前的代码。我认为这应该有效，因为如果它离开，它应该撤消其最后的操作。

谢谢

Answer 1

问题是这段代码：

tx = t.xcor()
ty = t.ycor()

if tx > right_bound or tx < left_bound:
    t.undo()
if ty > top_bound or ty < bottom_bound:
    t.undo()

位于文件的顶层，而它应该嵌入到 move_forward_keys() 和 move_back_keys() 函数中：

CURSOR_OFFSET = 6  # cursor hotspot closer to front than back

canvas = Tk.Canvas(master=self, width=300, height=300)
canvas.grid(row=2, column=2, columnspan=3, padx=50)

canvas.focus_set()

t = turtle.RawTurtle(canvas)
t.setheading(90)

left_bound = -(canvas.winfo_width() / 2)
right_bound = canvas.winfo_width() / 2
top_bound = canvas.winfo_height() / 2
bottom_bound = -(canvas.winfo_height() / 2)

def move_forward_keys(_):
    t.forward(9)
    tx, ty = t.position()

    if tx > right_bound or tx < left_bound:
        t.undo()

    if ty > top_bound or ty < bottom_bound:
        t.undo()

def move_left_keys(_):
    t.left(20)

def move_right_keys(_):
    t.right(20)

def move_back_keys(_):
    t.back(9)
    tx, ty = t.position()

    if tx > right_bound - CURSOR_OFFSET or tx < CURSOR_OFFSET + left_bound:
        t.undo()

    if ty > top_bound - CURSOR_OFFSET or ty < CURSOR_OFFSET + bottom_bound:
        t.undo()

canvas.bind("<Up>", move_forward_keys)
canvas.bind("<Left>", move_left_keys)
canvas.bind("<Right>", move_right_keys)
canvas.bind("<Down>", move_back_keys)

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