为什么tkinter window中没有出现按钮？

Question

I am currently trying to learn tkinter. I do not understand why the buttons I defined do not appear in this code:

from tkinter import *

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



            button1 = Button(self, text="Exit", width=12, command=self.clickButton1)

            button1.grid(row=0)

            button2 = Button(self, text="Test", width=12, command=self.clickButton2)

            button2.grid(row=1)

        def clickButton1(self):
            exit()

        def clickButton2(self):
            print("Nice")

root = Tk()
app = Window(root)
root.title("Tkinter window")

root.mainloop()

When I don't use a class it works. Like this for example:

from tkinter import *

root = Tk()

button1 = Button(root, text="Works!!!")
button1.grid(row=0)

button2 = Button(root, text="Also works!!!")
button2.grid(row=1)

root.mainloop()
´´´

Answer 1

The reason is that the class creates a frame, and then puts widgets inside the frame. However, you never add the frame to the window so the widgets inside the frame will be invisible.

You need to make sure and call pack , grid , or place on the instance of Window , just like you do with any other widget.

app = Window(root)
app.pack(fill="both", expand=True)