tkinter不会从其他方法将图像绘制到画布上。

例1有效,例2无效。有人能解释一下为什么吗?

例1

def init_gui(self):
    window = tkinter.Tk()
    self.canvas = tkinter.Canvas(self.window, width=1000, height=500)

    photo = PIL.ImageTk.PhotoImage(image=PIL.Image.fromarray(self.img))
    self.canvas.create_image(0, 0, image=photo, anchor=tkinter.NW)
    self.canvas.pack()

    window.mainloop()
    pass

例2

def init_gui(self):
    window = tkinter.Tk()
    self.canvas = tkinter.Canvas(self.window, width=1000, height=500)

    self._draw_img() # the exact same code, only in another method

    window.mainloop()
    pass
def _draw_img(self):
    photo = PIL.ImageTk.PhotoImage(image=PIL.Image.fromarray(self.img))
    self.canvas.create_image(0, 0, image=photo, anchor=tkinter.NW)
    self.canvas.pack()
    pass