python canvas在循环中创建图像

Question

您好，我最近开始学习 tkinter 并决定学习国际象棋棋盘游戏。下面是我的代码：import tkinter as tkclass 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)上面的代码我是将一块（黑车）添加到板上，它按预期工作。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 pawn 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 Pawn 块。请建议/帮助我理解这个问题。

Answer 1

垃圾收集器正在销毁 python 图像对象。您需要保存对图像的引用。第一次通过循环，bname保存对创建的第一个图像的引用。在下一次迭代中，bname修改为引用第二个图像。因此，第一张图像不再有参考。

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)

        ...