Python：如何在 tkinter 窗口中居中标签

Question

I'm trying to construct a popup window, containing varying text message for user to respond.

I seek a way to center the text (Label) and Button inside that window- with no success.

Popup Window has a determind size. Centering the frame inside it should take into account width and height of textlabel ( defined in amount of letters ).

As you can see in code, w , h defines window's size, xbias , ybias have an expression to center testframe (both contains alpha1 , alpha2 as a correction factor for text's size )

I'm seeking the mathematical expression for alpha1 , alpha2 ( which equal for 1 for now )... or a better way to construct such a popup window.

root = Tk()
w = '400'
h = '100'
root.geometry('{}x{}'.format(w, h))
root.configure(bg='lightgreen')

txt = StringVar()
txt.set("This is an error message")

alpha1 = 1
alpha2 = 1
xbias = int(w) / 2 - (len(txt.get()) / 2) * alpha1
ybias = int(h) / 2 - alpha2

testframe = ttk.Frame(root)
testframe.grid(row=0, column=1, pady=ybias, padx=xbias)

label1 = ttk.Label(testframe, textvariable=txt)
label1.grid(row=0, column=0)

Answer 1

Have you considered using the .pack() method instead for this. You could achieve the desired effect far easier that way:

from tkinter import *

root = Tk()
top = Toplevel(root)

w = '400'
h = '100'
top.geometry('{}x{}'.format(w, h))

frame = Frame(top)

label = Label(frame, text="This is an error message")
button = Button(frame, text="Ok")

frame.pack(expand=True) #expand assigns additional space to the frame if the parent is expanded
label.pack()
button.pack()

root.mainloop()

---

After some research, doing this with grid is an awful lot easier than expected, see below:

from tkinter import *

root = Tk()

w = '400'
h = '100'
root.geometry('{}x{}'.format(w, h))

label = Label(root, text="text")
label.grid(column=0, row=0)
root.columnconfigure(0, weight=1)
root.rowconfigure(0, weight=1)

root.mainloop()

If we assign .rowconfigure() and .columnconfigure() a weight which is not 0 then the specified row and column will expand to fill the space given to it in the window.

Answer 2

A way to center Frame inside root window can be done in this manner:

Part A) Create A window with a specific size h , w (since it is a popup - in this example I disable resizing it ). Inside the frame- a Label and a Button :

root = Tk()
w = '200'
h = '80'
root.geometry('{}x{}'.format(w, h))
root.configure(bg='lightgreen')    ###To diff between root & Frame
root.resizable(False, False)

txt = StringVar()
txt.set("This is an error message")

testframe = ttk.Frame(root)
testframe.grid(row=0, column=1)

label1 = ttk.Label(testframe, textvariable=txt)
label1.grid(row=0, column=0, pady=10)

ok_button = ttk.Button(testframe, text="OK", command=root.destroy)
ok_button.grid()

Part B) In order to get frame's dimensions ( including Label and Button inside ) we use testframe.update() and then testframe.winfo_width() testframe.winfo_height() to obtain frame's updated values. xbias and ybias calculates the center to place the frame in the middle:

testframe.update()

xbias = int(w) / 2 - testframe.winfo_width() / 2
ybias = int(h) / 2- testframe.winfo_height() / 2
testframe.grid(row=0, column=1, pady=ybias, padx=xbias)

root.mainloop()

Answer 3

A little late but I've found that using the anchor makes it easier to center a label in the window.

from tkinter import *

root = Tk()
w = 100
h = 100
root.geometry(f"{w}x{h}")

label = Label(root, text="text")
label.place(anchor=CENTER, relx=0.5, rely=0.5)

root.mainloop()