Tkinter focus_set and focus_force not working as expected

Question

I am attempting to have the Entry field to have focus when a new page opens up:

import tkinter as tk
from tkinter import *
from tkinter import ttk

class DIS(tk.Tk):

    def __init__(self, *args, **kwargs):
        tk.Tk.__init__(self, *args, **kwargs)
        tk.Tk.iconbitmap(self, default="")
        tk.Tk.wm_title(self, "program")
        container = tk.Frame(self)
        container.pack(side="top", fill="both", expand = True)
        container.grid_rowconfigure(0, weight = 1)
        container.grid_columnconfigure(0, weight = 1)

        self.frames = {}

        for F in (startPage, contactQues):
            frame = F(container, self)
            self.frames[F] = frame
            frame.grid(row = 0, column = 0, sticky = "nsew")
            self.show_frame(startPage)

    def show_frame(self, cont):
        frame = self.frames[cont]
        frame.tkraise()

class startPage(tk.Frame):
    def __init__(self, parent, controller):
        tk.Frame.__init__(self, parent)
        button2 = ttk.Button(self, text = "Here's a Button",
                    command=lambda: controller.show_frame(contactQues))
        button2.pack()

class contactQues(tk.Frame):

    def __init__(self, parent, controller):
        tk.Frame.__init__(self, parent)  
        self.controller = controller

        entry = Entry(self)
        entry.focus_force()
        entry.pack()

app = DIS()
app.mainloop()

If I move the Entry field under startPage, the focus is set correctly -- whenever I move it to contactQues, it loses the focus. Possibly a Toplevel issue?

Answer 1

It seems like tkraise() messes up the focus. So you need to invoke it after you've raised the page into view. I'd update you framework to always call some method after tkraise like so:

import tkinter as tk
from tkinter import *
from tkinter import ttk

class DIS(tk.Tk):

    def __init__(self, *args, **kwargs):
        tk.Tk.__init__(self, *args, **kwargs)
        tk.Tk.iconbitmap(self, default="")
        tk.Tk.wm_title(self, "program")
        container = tk.Frame(self)
        container.pack(side="top", fill="both", expand = True)
        container.grid_rowconfigure(0, weight = 1)
        container.grid_columnconfigure(0, weight = 1)

        self.frames = {}

        for F in (startPage, contactQues):
            frame = F(container, self)
            self.frames[F] = frame
            frame.grid(row = 0, column = 0, sticky = "nsew")
            self.show_frame(startPage)

    def show_frame(self, cont):
        frame = self.frames[cont]
        frame.tkraise()
        frame.postupdate()

class startPage(tk.Frame):
    def __init__(self, parent, controller):
        tk.Frame.__init__(self, parent)
        button2 = ttk.Button(self, text = "Here's a Button",
                    command=lambda: controller.show_frame(contactQues))
        button2.pack()

    def postupdate(self):
        pass

class contactQues(tk.Frame):

    def __init__(self, parent, controller):
        tk.Frame.__init__(self, parent)  
        self.controller = controller

        self.entry = Entry(self)
        self.entry.pack()

    def postupdate(self):
        self.entry.focus()

app = DIS()
app.mainloop()

If you want to avoid having the postupdate() method where it's not needed, you could check to see if it exists in the class before trying to run it. Like so:

def show_frame(self, cont):
    frame = self.frames[cont]
    frame.tkraise()
    try:
        frame.postupdate()
    except AttributeError:
        pass