Tkinter程序中tree.jpg图片无法显示问题排查求助

核心问题：PhotoImage对象被垃圾回收 #

你在问答界面创建Label时，直接把ImageTk.PhotoImage()的临时对象传给image参数，没有将这个对象保存为实例属性。Python的垃圾回收机制会自动清理无引用的临时对象，导致Label找不到图片资源，自然无法显示。

修复步骤 #

1. 保存PhotoImage引用
   在question类的__init__方法中，把创建的PhotoImage对象赋值给self的属性，让它持续被引用：

   # 原错误代码
   # test = Label(self, image=ImageTk.PhotoImage((PIL.Image.open(r"tree.jpg").resize((50,50)))))
   # 修改后
   self.img = ImageTk.PhotoImage(PIL.Image.open("tree.jpg").resize((50,50)))
   test = Label(self, image=self.img)
   

2. 优化窗口创建方式（可选但推荐）
   原代码登录成功后销毁主窗口再新建Tk()实例，不符合Tkinter设计规范，容易引发异常。建议改用Toplevel创建子窗口：

   # 修改login方法
   def login(self):
       if self.pwrd.get()=="a":
           # 隐藏登录窗口，创建子窗口
           self.master.withdraw()
           b = Toplevel()
           b.geometry(f"{width}x{height}")
           app_b = question(b)
           # 关闭子窗口时恢复登录窗口（可选）
           def on_close():
               b.destroy()
               self.master.deiconify()
           b.protocol("WM_DELETE_WINDOW", on_close)
       else:
           messagebox.showinfo("ERROR ","retry wrong password")
   

完整修复后的代码 #

from PIL import ImageTk
import PIL.Image

from tkinter import*
from tkinter import messagebox

class login_interface(Frame):
    def __init__(self,master=None):
        Frame.__init__(self,master)
        self.master=master
        self.security()

    def security(self):
        self.master.title("LOGIN")
        self.pack(fill=BOTH, expand=1)
        lbl = Label(self, text="PASSWORD").grid(column=0, row=0)
        self.pwrd = Entry(self,show="*")
        self.pwrd.focus_set()
        self.pwrd.grid(column=1, row=0)
        login = Button(self, text="login", width=20,command=self.login)
        login.grid(column=1, row=2)

    def login(self):
        if self.pwrd.get()=="a":
            self.master.withdraw()
            b = Toplevel()
            b.geometry(f"{width}x{height}")
            app_b=question(b)
            # 关闭问答窗口时恢复登录窗口
            def on_close():
                b.destroy()
                self.master.deiconify()
            b.protocol("WM_DELETE_WINDOW", on_close)
        else:
            messagebox.showinfo("ERROR ","retry wrong password")

class question(Frame):
    def __init__(self,master=None):
        Frame.__init__(self,master)
        self.master=master

        self.master.title("Question")
        self.pack(fill=BOTH, expand=1)
        # 保存PhotoImage引用到实例属性
        self.img = ImageTk.PhotoImage(PIL.Image.open("tree.jpg").resize((50,50)))
        test = Label(self, image=self.img)
        test.pack()
        lbl = Label(self, text="Who made the pythagoras theorem?").place(relx=0.5, rely=0.3, anchor='center')
        self.my_guess = Entry(self)
        self.my_guess.place(relx=0.5, rely=0.5, anchor='center')
        my_enter = Button(self, text="Enter", command=self.check).place(relx=0.5, rely=0.7, anchor='center')

    def check(self):
        if self.my_guess.get() == "Pythagoras":
            messagebox.showinfo("Correct","Go to Next Quiz.")
        else:
            messagebox.showinfo("Wrong", "Try Again.")

a=Tk()
width= a.winfo_screenwidth()
height= a.winfo_screenheight()
a.geometry(f"{width}x{height}")
app=login_interface(a)
app.mainloop()

内容的提问来源于stack exchange，提问作者ADS