How to make tkinter toggle button class by deriving from tkinter.Button? - python-3.x

Question

I am trying to make a toggle button class by deriving from the tkinter.Button object. To that end, I am using this StackOverflow answer and these code examples.
The problem is that I get my desired toggle behavior from the button only after I click it twice; the first two clicks, it does not enact the self.config(relief="sunken"). I tried using the command keyword argument sample from this answer and that works from the start.
import tkinter as tk
class ToggleButton(tk.Button):
def __init__(self, parent=None, toggle_text="Toggled", toggle_bg_color="green", **kwargs):
tk.Button.__init__(self, parent, **kwargs)
self.toggled = False
self.default_bg_color = self['bg']
self.default_text = self["text"]
self.toggle_bg_color = toggle_bg_color
self.toggle_text = toggle_text
self.bind("<Button-1>", self.toggle, add="+")
def toggle(self, *args):
if self["relief"] == "sunken":
self["bg"] = self.default_bg_color
self["text"] = self.default_text
self.config(relief="raised")
# self["relief"] = "raised"
self.toggled = False
else:
self["bg"] = self.toggle_bg_color
self["text"] = self.toggle_text
# self["relief"] = "sunken"
self.config(relief="sunken")
self.toggled = True
def button_placeholder():
print("TO BE IMPLEMENTED")
root = tk.Tk()
button = ToggleButton(parent=root,
toggle_text="ON", toggle_bg_color="green",
text="OFF", command=button_placeholder)
button.pack()
root.mainloop()
Here are screenshots of the behavior of the buttons after numerous clicks
After the first two clicks on the button, the expected behavior occurs. However, if the user focuses on another window (for instance by minimizing the tkinter window) and then back, again the first two clicks do not cause the desired behavior.
Can some explain this? If not, can someone provide a solution where I can have consistent behavior on toggling my button?
Information about my system
Windows 10; 64 bit
Python 3.7.3 (64 bit)
Tkinter 8.6

Answer 1

The problem you seem to have is that the bg parameter is not defined when you first create the button; it only gets a value assigned upon the first button press.
Then, the logic to toggle is hard to follow: you have a self.toggled boolean, yet you are testing if the button is sunken or not to differentiate between states...
I reorganized the logic to make it easier to follow; after all, toggle is a binary change from one state to another. I therefore placed the definition of the ON and OFF states in the body of the class (into two class dictionaries), and the code swaps the two configs upon toggling.
On Windows:
import tkinter as tk
class ToggleButton(tk.Button):
ON_config = {'bg': 'green',
'text': 'button is ON',
'relief': 'sunken',
}
OFF_config = {'bg': 'white',
'text': 'button is OFF',
'relief': 'raised',
}
def __init__(self, parent, *args, **kwargs):
super().__init__(parent, *args, **kwargs)
self.toggled = False
self.config = self.OFF_config
self.config_button()
self.bind("<Button-1>", self.toggle)
def toggle(self, *args):
if self.toggled: # True = ON --> toggle to OFF
self.config = self.OFF_config
else:
self.config = self.ON_config
self.toggled = not self.toggled
return self.config_button()
def config_button(self):
self['bg'] = self.config['bg']
self['text'] = self.config['text']
self['relief'] = self.config['relief']
return "break"
def __str__(self):
return f"{self['text']}, {self['bg']}, {self['relief']}"
def button_placeholder():
print('toggling now!')
if __name__ == '__main__':
root = tk.Tk()
button = ToggleButton(root)
button.pack()
root.mainloop()
On OSX:
Where the buttons aspect is fixed, using a tk.Label can mimic the desired behavior:
import tkinter as tk
class ToggleButtonLBL(tk.Label):
ON_config = {'bg': 'green',
'text': 'button is ON',
'relief': 'sunken',
}
OFF_config = {'bg': 'white',
'text': 'button is OFF',
'relief': 'raised',
}
def __init__(self, parent, *args, command=None, **kwargs):
super().__init__(parent, *args, **kwargs)
self.toggled = False
self.config = self.OFF_config
self.config_button()
self.bind("<Button-1>", self._toggle_helper)
self.bind("<ButtonRelease-1>", self._toggle)
self.command = command
def _toggle_helper(self, *args):
return 'break'
def _toggle(self, dummy_event):
self.toggle()
self.cmd()
def toggle(self, *args):
if self.toggled: # True = ON --> toggle to OFF
self.config = self.OFF_config
else:
self.config = self.ON_config
self.toggled = not self.toggled
self.config_button()
return 'break'
def config_button(self):
self['bg'] = self.config['bg']
self['text'] = self.config['text']
self['relief'] = self.config['relief']
return "break"
def __str__(self):
return f"{self['text']}, {self['bg']}, {self['relief']}"
def cmd(self):
self.command()
def button_placeholder():
print('toggling now!')
if __name__ == '__main__':
root = tk.Tk()
button = ToggleButtonLBL(root, command=button_placeholder)
button.pack()
root.mainloop()