由于类结构，Tkinter 返回键绑定不起作用

Question

I understand how to bind keys when it's just on a simple frame but since I built my app in a different way, I can't seem to figure out how to bind the return key to press the button or run the function that the button is bounded to. I've been searching for a similar question by others on the website but I haven't found one similar to mine.

I've toned down the rest of my code and have it below:

import tkinter as tk
from tkinter import *

class POS(tk.Tk):
    def __init__(self,*args,**kwargs):
        tk.Tk.__init__(self, *args, **kwargs)

        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 (ErrorPage, MainPage):
            frame = F(container, self)
            self.frames[F] = frame
            frame.grid(row=0, column = 0, sticky = "nsew")

        self.show_frame(MainPage)

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


class MainPage(tk.Frame):
    def __init__(self, parent, controller):
        tk.Frame.__init__(self,parent)
        frame = tk.Frame(self)
        frame.pack(fill = BOTH)

        button = Button(frame, text = "OK", command = self.bindHello)
        button.pack(pady=5, padx=10)

        frame.bind("<Return>", self.bindHello)
        self.bind("<Return>", self.bindHello)

    def bindHello(self, event=None):
        print("HELLO1")


#Yes this doesn't do anything but I need it for the frame container as set before
class ErrorPage(tk.Frame):
    def __init__(self, parent, controller):
        tk.Frame.__init__(self,parent)
        frame = tk.Frame(self)
        frame.pack(fill = BOTH)

        button = Button(frame, text = "OK", command = self.bindHello)
        button.pack(pady=5, padx=10)

        frame.bind("<Return>", self.bindHello)

    def bindHello(self, event=None):
        print("HELLO2")


app = POS()
app.mainloop()

Simple Button bind I had intended to work as is as follows:

from tkinter import *
master = Tk()

def callback(event=None):
    print("Hello " + entry.get())

entry = StringVar()
e = Entry(master, textvariable = entry, width = 15)
e.pack()

b = Button(master, text="OK", command = callback)
b.pack()
master.bind("<Return>", callback)

mainloop()

I would just like to have a simple button bind like the one above but I can't seem to find a way for my main program to work. I think it's due to the way I structured my app, but I'm not entirely sure.

Answer 1

On your sample you bind to the window itself. You can do so in the other one as well in a number of ways:

#1 bind to page object's direct parent, which happens to be a Toplevel-like
#self.master.bind('<Return>', self.bindHello)

#2 recursively search page object's parents, and bind when it's a Toplevel-like
#self.winfo_toplevel().bind('<Return>', self.bindHello)

#3 bind to page object's inner frame's parent's parent, which happens to be a Toplevel-like
#frame.master.master.bind('<Return>', self.bindHello)

#4 recursively search page object's inner frame's parents, and bind when it's a Toplevel-like
frame.winfo_toplevel().bind('<Return>', self.bindHello)