python canvas 循环创建图像

Question

你好，我最近开始学习 tkinter 并决定学习棋盘游戏。
下面是我的代码：

import tkinter as tk

class GameBoard(tk.Frame):
    def __init__(self, parent, rows=8, columns=8, size=70, color1="white", color2="blue"):
        '''size is the size of a square, in pixels'''

        self.rows = rows
        self.columns = columns
        self.size = size
        self.color1 = color1
        self.color2 = color2
        self.pieces = {}

        canvas_width = columns * size
        canvas_height = rows * size

        tk.Frame.__init__(self, parent)
        self.canvas = tk.Canvas(self, borderwidth=0, highlightthickness=0,
                                width=canvas_width, height=canvas_height, background="bisque")
        self.canvas.pack(side="top", fill="both", expand=True, padx=2, pady=2)

root = tk.Tk()
board = GameBoard(root)
board.pack(side="top", fill="both", expand="true", padx=4, pady=4)

black_rook_l = tk.PhotoImage(file=black_rook_img)
black_rook_l = black_rook_l.subsample(2, 2)
board.addpiece("black_rook_l", black_rook_l, 0,0)

上面的代码我是将棋子（黑车）添加到棋盘上，这是按预期工作的。
下面是辅助函数：

def addpiece(self, name, image, row=0, column=0):
    '''Add a piece to the playing board'''
    self.canvas.create_image(0,0, image=image, tags=(name, "piece"), anchor="c")
    self.placepiece(name, row, column)

def placepiece(self, name, row, column):
    '''Place a piece at the given row/column'''
    self.pieces[name] = (row, column)
    x0 = (column * self.size) + int(self.size/2)
    y0 = (row * self.size) + int(self.size/2)
    # print(name, x0, y0)
    self.canvas.coords(name, x0, y0)

但是当我尝试在 for 循环的帮助下放置棋子时出现问题。下面是代码：

for i in range(8):
    bname = tk.PhotoImage(file=black_pawn_img)
    bname = bname.subsample(2, 2)
    board.addpiece("black_pawn_"+str(i), bname, 1,i)

root.mainloop()

它只放置最后一个棋子。

请suggest/help我理解这个问题。
提前致谢。

Answer 1

python 图像对象正在被垃圾收集器销毁。您需要保存对图像的引用。第一次通过循环时，bname 持有对创建的第一个图像的引用。在下一次迭代中，bname 被修改为引用第二张图像。因此，第一张图片不再有参考。

一种简单的方法是在创建它们的代码块中跟踪它们：

images = []
for i in range(8):
    bname = tk.PhotoImage(file=black_pawn_img)
    bname = bname.subsample(2, 2)
    board.addpiece("black_pawn_"+str(i), bname, 1,i)
    images.append(bname)

另一种方法是 addpiece 保存它们：

class GameBoard(...):
    def __init__(...):
        ...
        self.images = []
        ...
    def addpiece(self, name, image, row=0, column=0):
        ...
        self.images.append(image)
        ...

python canvas 循环创建图像

python canvas create image in loop

python

tkinter

python-3.x

tkinter-canvas

python-chess