The problem I'm running into here is that, when I click on the different file names in the Listbox, the Label changes value one click behind whatever I'm currently clicking on.
What am I missing here?
import Tkinter as tk
class TkTest:
def __init__(self, master):
self.fraMain = tk.Frame(master)
self.fraMain.pack()
# Set up a list box containing all the paths to choose from
self.lstPaths = tk.Listbox(self.fraMain)
paths = [
'/path/file1',
'/path/file2',
'/path/file3',
]
for path in paths:
self.lstPaths.insert(tk.END, path)
self.lstPaths.bind('<Button-1>', self.update_label)
self.lstPaths.pack()
self.currentpath = tk.StringVar()
self.lblCurrentPath = tk.Label(self.fraMain, textvariable=self.currentpath)
self.lblCurrentPath.pack()
def update_label(self, event):
print self.lstPaths.get(tk.ACTIVE),
print self.lstPaths.curselection()
self.currentpath.set(self.lstPaths.get(tk.ACTIVE))
root = tk.Tk()
app = TkTest(root)
root.mainloop()
The problem has to do with the fundamental design of Tk. The short version is, bindings on specific widgets fire before the default class bindings for a widget. It is in the class bindings that the selection of a listbox is changed. This is exactly what you observe -- you are seeing the selection before the current click.
The best solution is to bind to the virtual event <<ListboxSelect>> which is fired after the selection has changed. Other solutions (unique to Tk and what gives it some of its incredible power and flexibility) is to modify the order that the bindings are applied. This involves either moving the widget bindtag after the class bindtag, or adding a new bindtag after the class bindtag and binding it to that.
Since binding to <<ListboxSelect>> is the better solution I won't go into details on how to modify the bindtags, though it's straight-forward and I think fairly well documented.
Related
I have been trying to represent tkinter window in an OO manner. There are few answers here, and I have managed to produce a working code, but I simply do not understand why it's working.
import tkinter as tk
class CurrConv:
def __init__(self, window, date):
self.window = window
window.title("Currency Converter")
window.geometry("350x150+300+300")
self.label = tk.Label(text="Date: {}\n".format(date))
self.label.pack()
self.text_box = tk.Text()
self.text_box.insert("2.0", "100 is: {}\n".format(100))
self.text_box.insert("3.0", "24 is: {}".format(24))
self.text_box.pack()
self.button = tk.Button(text="Quit", width=8, command=window.quit)
self.button.place(relx=0.5, rely=0.9, anchor="center",)
def main():
window = tk.Tk()
app = CurrConv(window, 1234)
window.mainloop()
if __name__ == "__main__":
main()
The thing I don't understand is the usage of "app" object. It is used nowhere, and usually when we create an object (in any programing language), we invoke certain actions on it. However here we do nothing with the app object. Class encapsulation appears to indirectly modify "window", which is confusing, to say the least.
Next, I don't understand how labels and text boxes are added to "window", when in the code I nowhere create those in "window", I create them on "self", which would be "app", which is no longer used.
Bottom line is, for the reasons above, I do not understand how the above code works.
Thanks in advance.
I hope I was clear enough.
Class encapsulation appears to indirectly modify "window", which is confusing, to say the least.
Yes, that is what the code is doing, and it's incorrect IMHO. The code inside of CurrConv.__init__ at least arguably should not be directly modifying the root window for some of the very reasons you put in your question.
Next, I don't understand how labels and text boxes are added to "window", when in the code I nowhere create those in "window", I create them on "self", which would be "app", which is no longer used.
Your terminology is a bit incorrect. "I nowhere create those in 'window'" isn't true. By creating the widgets without an explicit master they default to being created in the root window. The reference to the widget is created in the class (self.label, etc) but the widget itself is created in the root window. IMHO this is also not the proper way to write a tkinter application. Explicit is better than implicit.
For me, the proper way to write this class would be for CurrConv to inherit from a tkinter Frame (or some other widget). Everything it creates should go inside itself, and then the code that creates the instance of CurrConv is responsible for adding it to a window. This solves your problem of not being able to create multiple windows.
Also, the widgets inside of CurrConv should explicitly set the master of any child widgets it creates rather than relying on a default master.
Example:
class CurrConv(tk.Frame):
def __init__(self, window, date):
super().__init__(window)
self.label = tk.Label(self, ...)
self.text_box = tk.Text(self, ...)
self.button = tk.Button(self, ...)
...
...
With that, everything is nicely encapsulated inside the class, and you can create multiple instances inside multiple windows very easily:
root = tk.Tk()
conv1 = CurrConv(root)
conv1.pack(fill="both", expand=True)
top = tk.Toplevel(root)
conv2 = CurrConv(top)
conv2.pack(fill="both", expand=True)
In the above case, it's perfectly fine for the class to modify the window because it's part of the code that creates the window in the first place.
You can still use a class for the application as a whole which you can use to hold some global state. To further prove the usefulness of creating CurrConv as a subclass of Frame, the following example adds currency converters to a notebook instead of separate windows.
class CurrConvApp():
def __init__(self):
self.root = tk.Tk()
self.root.title("Currency Converter")
self.root.geometry("350x150+300+300")
self.notebook = ttk.Notebook(self.root)
cc1 = CurrConv(self.notebook)
cc2 = CurrConv(self.notebook)
self.notebook.add(cc1, text="USD to EUR")
self.notebook.add(cc2, text="EUR to USD")
...
def start(self):
self.root.mainloop()
if __name__ == "__main__":
app = CurrConvApp()
app.start()
For the first question, yes app is an object. But it is an instance of the class CurrConv. When you initialize a class, you call the class's __init__ method, and this case, by doing so, you execute the statements in that method: modifying the window (which you passed as a parameter whin you created app) and adding widgets to it. So although app is not directly used, it had the side effect of doing those things when it was created. And for that reason, since you only need the initialization method, assigning to a variable is not necessary, you can just make it like CurrConv(window, 1234).
For the second, yes, you didn't mention window when you created the widgets, but when the master of a new Tkinter widget is not specified, it takes the main master (the root, created using tk.Tk()) as it's master.
So I have an app in Tkinter that has a lot of buttons in the first screen and when you press one you pass into a new "Window" (basically destroying all widgets and drawing the ones that are needed for the 'window'). There is a standard function that uses some commands to destroy every child on the root. I would like to add some code that can unbind all of the bindings that are made in the root. Bindings that are on specific widgets get destroyed but those that are bind on the root stay there and cause error.
Here's the code for destroying the widgets.
#staticmethod
def clear():
for widget in guihandle.root.winfo_children():
widget.destroy()
#staticmethod
def set(db,table):
guihandle.clear()
curW = Window(db,table)
guihandle.current_Window = curW
curW.initialize()
guihandle.windows.push(curW)
(Yes, I make the base GUI from a sqlite3 database :P)
There is nothing in Tkinter to do what you want. Your app will need to keep track of the bindings it wants to remove.
That being said, depending on just how complex your real problem is, there may be other solutions. For example, instead of binding to the root window, bind to a custom binding tag (also called a bind tag or bindtag). You will then need to add that tag to every widget to enable the bindings, and remove the tag from any existing widgets to effectively disable the bindings.
I know I am VERY late but, if you go through your code and replace every widget.bind with the function below, which was taken and modified from here
def bindWidget(widget: Widget, event, all:bool=False, func=None):
# https://stackoverflow.com/a/226141/19581763
'''Set or retrieve the binding for an event on a widget'''
try:
_ = widget.__dict__['bindings']
except KeyError:
has_binding_key = False
else:
has_binding_key = True
if not has_binding_key:
setattr(widget, 'bindings', dict())
if func:
if not all:
widget.bind(event, func)
else:
widget.bind_all(event, func)
widget.bindings[event] = func
else:
return(widget.bindings.setdefault(event, None))
Than the function will keep track of every binding for you by setting a attribute called bindings which has both, the event and the function inside of it.
For example:
label.bind('<Button-1>', label.destroy)
Will become:
bindWidget(label, '<Button-1>', func=label.destroy)
After doing that, you can write a simple function which deletes all of the bindings and widgets:
def clear(self): # Self will be your Tk() instance
"""Clears everything on the window, including bindings"""
for child in self.winfo_children():
child.destroy()
if not hasattr(self, 'bindings'):
self.bindings = {}
for event, func in self.bindings.items():
self.unbind_all(event)
self.bindings = {}
There are only 2 caveats with this approach
Time
You will have to go through your code to replace every widget.bind and if you have lots of bindings, than it will take a lot of time
Readability
bindWidget(label, '<Button-1>', func=label.destroy) is less readable and less clear than label.bind('<Button-1>', label.destroy)
Edit 8/11/2022
Alternatively, you can destroy the entire window and recreate it like this:
window.destroy()
window = Tk()
However, I am not sure if creating a whole Tcl interpreter is good.
I created a Frame, gave it a menubar. Works just fine. The purpose of the entry in the menubar is to open a new frame, in which u can change some settings. The creation of the new Window works also. However I can't create widgets on the new created window. I tried it with a Button and got a
TclError: can't invoke "button" command: application has been destroyed
I tried to google it and found Cannot invoke button command: application has been destroyed which didn't quite helped me.
Further I found a solution were u have to create a parent class (which inherrits from Frame) and than create all other Frames within it, but on the first view it looked pretty complicated. Especially because the creation of the second window seems to work in the first place.
I know this is probably a really basic question, so thanks in advance for your time
def perfSettings():
perfFrame = Tk(className=" Performanz Einstellungen")
perfFrame.configure(bg='#F2F2F2')
perfFrame.geometry("300x300")
perfFrame.mainloop()
btn = Button(master=perfFrame, text='Speichern', command=myPerfSettingValue.getValues, width=37)
btn.pack()
# Button(perfFrame, text='Abbrechen', command=perfFrame.destroy, width=37).grid(row=0 ,column=1 )
class perfSettingsValue:
def __init__(self):
self.bvhSteps = 0
def getValues(self):
pass
#Hauptfenster
root = Tk(className="BoneMapping & SkeletonEstimation")
root.configure(bg='#F2F2F2')
root.geometry("1300x600")
myPerfSettingValue = perfSettingsValue()
menubar = Menu(root)
sdmenu = Menu(menubar, tearoff=0)
sdmenu.add_command(label="Performanz", command=perfSettings)
menubar.add_cascade(label='Einstellungen',menu=sdmenu)
root.config(menu=menubar)
The key problem here is that you are trying to add a button after starting the mainloop which effectively blocks the execution of the program. The error you are getting is because the line that adds the button gets executed after the window has been closed.
Your problem will be solved if you modify your function like this:
def perfSettings():
perfFrame = Tk(className=" Performanz Einstellungen")
perfFrame.configure(bg='#F2F2F2')
perfFrame.geometry("300x300")
btn = Button(master=perfFrame, text='Speichern', command=myPerfSettingValue.getValues, width=37)
btn.pack()
perfFrame.mainloop()
This is not the only problem though. Instead of creating a new instance of Tk, you should create a new Toplevel instance, which will, in your case, act just as a Tk instance, but have a lot less tendency to cause trouble.
Finally, you should consider reading on the object oriented approach to designing tkinter applications. There are far too many variants of that to be appropriately elaborated here but I certainly recommend you take the effort to learn to use one of them. It will make your code more comprehensible and maintainable. My usual approach is to create a class that inherits from Toplevel or Tk for every type of window I am going to use.
I'm proposing a continuation of the discussion in disable tkinter keyboard shortcut: I have an event handler for an event that Tkinter also uses, so that my prog & Tkinter interact badly.
Since it is a problem that I've been unable to solve I'm re-proposing here, where I tried to boil it down to the simplest form in the following code:
#!/usr/bin/env python
from Tkinter import *
import tkFont
def init():
global root,text
root = Tk()
root.geometry("500x500+0+0")
dFont=tkFont.Font(family="Arial", size=10)
text=Text(root, width=16, height=5, font=dFont)
text.pack(side=LEFT, fill=BOTH, expand = YES)
root.bind("<Control-b>", setbold)
text.tag_config("b",font=('Verdana', '10', 'bold' ))
text.tag_config("i",font=('Verdana', '10', 'italic' ))
def removeformat(event=None):
text.tag_remove('b',SEL_FIRST,SEL_LAST)
text.tag_remove('i',SEL_FIRST,SEL_LAST)
def setbold(event=None):
removeformat()
text.tag_add('b', SEL_FIRST,SEL_LAST)
text.edit_modified(True)
def main():
init()
mainloop()
if __name__ == '__main__':
main()
What it should do is simply to produce a text window where you write into.
Selecting some text and pressing Ctrl+B the program should remove any preexisting tag, then assign to it the 'b' tag that sets the text to bold.
What instead happens is an exception at the first tag_remove, telling me that text doesn't contain any characters tagged with "sel".
The suggestion to use a return 'break' is of no use, since the selection disappears before setbold() has any chance to act...
Set your binding on the text widget, not on the root. (Whole toplevel bindings are processed after widget class bindings – where the standard <Control-Key-b> binding is – and those are processed after the widget instance bindings, which is what you want to use here.) And you need to do that 'break'; it inhibits the subsequent bindings. (If you're having any problems after that, it's probably that the focus is wrong by default, but that's easy to fix.)
The only other alternative is to reconfigure the bindtags so that class bindings are processed after toplevel bindings, but the consequences of doing that are very subtle and far-reaching; you should use the simpler approach from my first paragraph instead as that's the normal way of handling these things.
Bindings are handled in a specific order, defined by the bindtags of that widget. By default this order is:
The specific widget
The widget class
The toplevel window
The special class "all"
If there are conflicting bindings -- for example, a control-b binding on both the widget and class -- they both will fire (in the described order) unless you break the chain by returning "break".
In the case of the code you posted, however, you are binding to the toplevel window (ie: the root window), and the conflicting binding is on the class. Therefore, the binding will fire for the class before it is processed by the toplevel, so even if your binding returned "break" it wouldn't matter since the class binding happens first.
The most straight-forward solution is to move your binding to the actual widget and return "break". That will guarantee your binding fires first, and the return "break" guarantees that the class binding does not fire.
If you really want your binding on the root window, you can remove the binding for the class using the bind_class method with the value of "Text" for the class.
You might find the Events and Bindings page on effbot.org to be useful.
I am re designing a portion of my current software project, and want to use hyperlinks instead of Buttons. I really didn't want to use a Text widget, but that is all I could find when I googled the subject. Anyway, I found an example of this, but keep getting this error:
TclError: bitmap "blue" not defined
When I add this line of code (using the IDLE)
hyperlink = tkHyperlinkManager.HyperlinkManager(text)
The code for the module is located here and the code for the script is located here
Anyone have any ideas?
The part that is giving problems says foreground="blue", which is known as a color in Tkinter, isn't it?
If you don't want to use a text widget, you don't need to. An alternative is to use a label and bind mouse clicks to it. Even though it's a label it still responds to events.
For example:
import tkinter as tk
class App:
def __init__(self, root):
self.root = root
for text in ("link1", "link2", "link3"):
link = tk.Label(text=text, foreground="#0000ff")
link.bind("<1>", lambda event, text=text: self.click_link(event, text))
link.pack()
def click_link(self, event, text):
print("You clicked '%s'" % text)
root = tk.Tk()
app = App(root)
root.mainloop()
If you want, you can get fancy and add additional bindings for <Enter> and <Leave> events so you can alter the look when the user hovers. And, of course, you can change the font so that the text is underlined if you so choose.
Tk is a wonderful toolkit that gives you the building blocks to do just about whatever you want. You just need to look at the widgets not as a set of pre-made walls and doors but more like a pile of lumbar, bricks and mortar.
"blue" should indeed be acceptable (since you're on Windows, Tkinter should use its built-in color names table -- it might be a system misconfiguration on X11, but not on Windows); therefore, this is a puzzling problem (maybe a Tkinter misconfig...?). What happen if you use foreground="#00F" instead, for example? This doesn't explain the problem but might let you work around it, at least...