为什么稍后声明的小部件首先出现？

Question

我正在使用Python的tkinter库来创建一个小型GUI。该应用程序的代码如下：

import tkinter as tk
from tkinter import ttk
APP_TITLE = "HiDE"

class Application(tk.Frame):
    """This class establishes an entity for the application"""
    #The constructor of this class
    def __init__(self, master=None):        
        tk.Frame.__init__(self,master)
        self.grid()

    def setupWidgets(self):
        self.message = tk.Label(self,text='Login')
        self.quitButton = tk.Button(self,text='Quit',command=self.quit)
        self.logButton = tk.Button(self,text='Login',command=self.quit)
        self.master.title(APP_TITLE)
        self.master.minsize("300","300")
        self.master.maxsize("300","300")
        self.message.grid()
        self.logButton.grid()
        self.quitButton.grid()

#Setting up the application
app = Application()
img = tk.PhotoImage(file='icon.png')
#getting screen parameters
w = h = 300#max size of the window
ws = app.master.winfo_screenwidth() #This value is the width of the screen
hs = app.master.winfo_screenheight() #This is the height of the screen

# calculate position x, y
x = (ws/2) - (w/2)
y = (hs/2) - (h/2)
#This is responsible for setting the dimensions of the screen and where it is placed
app.master.geometry('%dx%d+%d+%d' % (w, h, x, y))
app.master.tk.call('wm', 'iconphoto', app.master._w, img)
app.master.i_con = tk.Label(app.master, image=img)
app.master.i_con.grid()
app.setupWidgets()  #<-- This is the function call
app.mainloop()

在设置图像后调用setupWidgets函数，但输出为：

Answer 1

当您将Label与图像网格化时，您已经在类中的Frame上调用了网格。此类是放置其他小部件的位置，因此它位于带有图像的Label上方。

而不是

app.master.i_con = tk.Label(app.master, image=img)

试

app.master.i_con = tk.Label(app, image=img)

将带有图像的Label与其他小部件一起放在Frame中。

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另外，在没有指定行和列的情况下调用网格并没有多大意义。