Threading in Tkinter with Button Command-CodePudding

I'm building a tkinter app and as a part of it the user has to upload a file, write a message and then press a Button whose command runs in another thread.

self.sidebar_button = Button(self.sidebar_frame, text="send your message", 
                                                        command=threading.Thread(target=send_msg).start)

If the Button is pressed in the right condition then everything is fine. However, if the user doesn't upload the file and write the message before pressing the Button then i show the user an error message. The problem here is that since the first Button press has started the thread, it can't start again. Can you think of a workaround for this problem? Is it possible to disable the Button before the right conditions are met?

CodePudding user response：

try this:


root = Tk()

message = Entry(root)

def thread():
    while True:
        if message.get():
            butt.config(state=NORMAL)
        else:
            butt.config(state=DISABLED)


butt = Button(root , text= 'continue', state = DISABLED)
butt.pack()
Thread(target=thread).start()

CodePudding user response：

Look at this:

import tkinter as tk

# This is called each time there is a change in the entry
def check_conditions(*args):
    message_text = message_var.get()
    # Here we check the conditions:
    if message_text == "":
        button.config(state="disabled")
    else:
        button.config(state="normal")

def send():
    message_text = message_var.get()
    print(f"Send: {message_text!r}")

root = tk.Tk()

message_var = tk.StringVar(root)
# When the value of the `message_var` has changed, call `check_conditions`
message_var.trace("w", check_conditions)

# Create the entry and attach `message_var`
message = tk.Entry(root, textvariable=message_var)
message.pack()

button = tk.Button(root, text="Send", command=send, state="disabled")
button.pack()

root.mainloop()

It uses <tk.StringVar>.trace("w", <function>) to call check_conditions each time the user changes the entry. For more info, read this.

tkinter doesn't always like being called from other threads, so avoid using threading when using tkinter.