Python tkinter disable the button until all the fields are filled

问题

Let's say I have 2 entry widgets, 1 option menu(drop down list) and 1 button in tkinter. How can i set the button widget state to DISABLED until all 3 widgets are filled by the user?This is what i have currently:

import Tkinter as tk

root = tk.Tk()

entry1=tk.Entry(root,width=15).grid(row=1,column=1)
entry2=tk.Entry(root,width=15).grid(row=1,column=2)

choices=('a','b','c')
var=tk.StringVar(root)
option=tk.OptionMenu(root,var,*choices)
option.grid(row=1,column=3)

button=tk.Button(root,text="submit")
button.grid(row=1,column=4)

root.mainloop()

--EDIT--

Tried this way, but i don't think this is the correct way to do it.

import Tkinter as tk

root = tk.Tk()
def myfunction(event):
    x=var.get()
    y=entry1.get()
    z=entry2.get()
    print len(x),":",len(y),":",len(z)
    if len(y)>0 and len(x)>0 and len(z)>0:
        button.config(state='normal')
    else:
        button.config(state='disabled')
entry1=tk.Entry(root,width=15)
entry1.grid(row=1,column=1)
entry2=tk.Entry(root,width=15)
entry2.grid(row=1,column=2)

choices=('a','b','c')
var=tk.StringVar(root)
option=tk.OptionMenu(root,var,*choices)
option.grid(row=1,column=3)

button=tk.Button(root,text="submit")
button.grid(row=1,column=4)

root.bind("<Enter>", myfunction)
root.mainloop()

回答1:

Tkinter variables have a method called trace to add an observer, so the callback function is called when the value changes. I think it is much more efficient than root.bind("<Enter>", myfunction):

import Tkinter as tk

root = tk.Tk()

def myfunction(*args):
    x = var.get()
    y = stringvar1.get()
    z = stringvar2.get()
    if x and y and z:
        button.config(state='normal')
    else:
        button.config(state='disabled')

stringvar1 = tk.StringVar(root)
stringvar2 = tk.StringVar(root)
var = tk.StringVar(root)

stringvar1.trace("w", myfunction)
stringvar2.trace("w", myfunction)
var.trace("w", myfunction)

entry1 = tk.Entry(root, width=15, textvariable=stringvar1)
entry1.grid(row=1,column=1)
entry2 = tk.Entry(root, width=15, textvariable=stringvar2)
entry2.grid(row=1,column=2)

choices = ('a','b','c')
option = tk.OptionMenu(root, var, *choices)
option.grid(row=1,column=3)

button = tk.Button(root,text="submit")
button.grid(row=1, column=4)

root.mainloop()

回答2:

What about validate and validatecommand properties of Entry ?

#!/usr/bin/env python3

import tkinter


class App:

    def __init__(self):
        self.root = tkinter.Tk()
        self.variables = {}
        self.entries = {}
        self.vcmd = (self.root.register(self.observer), '%W', '%P')

        self.make_entry('fname')
        self.make_entry('sname')
        self.make_submit_button('Send')

    def make_entry(self, name):
        self.variables[name] = tkinter.StringVar()
        self.entries[name] = tkinter.Entry(
            self.root,
            textvariable=self.variables[name],
            validate='all',
            validatecommand=self.vcmd)
        self.entries[name].pack(side=tkinter.TOP)

    def make_submit_button(self, text):
        self.submit_button = tkinter.Button(
            self.root,
            text=text,
            state=tkinter.DISABLED)
        self.submit_button.pack(side=tkinter.BOTTOM)

    def observer(self, id_, value):
        id_ = int(id_[1:])
        self.update_submit_button_state(entry_exclude=(value and id_ or None))
        return True

    def update_submit_button_state(self, entry_exclude=None):
        if all(
            var.get() 
            for name, var in self.variables.items()
            if id(self.entries[name]) != entry_exclude
        ):
            self.submit_button.config(state=tkinter.NORMAL)
        else:
            self.submit_button.config(state=tkinter.DISABLED)


App().root.mainloop()

回答3:

Try this:

import Tkinter as tk

root = tk.Tk()
def myfunction(*event):
    x=var.get()
    y=entry1.get()
    z=entry2.get()
    print len(x),":",len(y),":",len(z)
    if len(y)>0 and len(x)>0 and len(z)>0:
        button.config(state='normal')
    else:
        button.config(state='disabled')
entry1=tk.Entry(root,width=15)
entry1.grid(row=1,column=1)
entry2=tk.Entry(root,width=15)
entry2.grid(row=1,column=2)

choices=('a','b','c')
var=tk.StringVar(root)
option=tk.OptionMenu(root,var,*choices)
option.grid(row=1,column=3)

button=tk.Button(root,text="submit")
button.grid(row=1,column=4)
button.config(state='disabled')

root.bind_class("Entry","<FocusOut>",myfunction)
var.trace('w', myfunction)
root.mainloop()

来源：https://stackoverflow.com/questions/16687124/python-tkinter-disable-the-button-until-all-the-fields-are-filled