Tkinter Scrollbar not working

Question

I have a piece of tkinter code running on python 3.4 that is a large frame placed in a canvas with a vertical scrollbar, however the scrollbar is grayed out and doesn't seem to be linked to the size of the frame. The code I'm using is essentially:

class EntryWindow:
    def __init__(self, master):
        self.master = master
        self.master.minsize(750, 800)
        self.master.maxsize(1000, 800)
        self.canvas = tk.Canvas(self.master, borderwidth=0, bg='#ffffff')
        self.vsb = tk.Scrollbar(self.master)
        self.master_frame = tk.Frame(self.canvas)
        self.vsb.pack(side="right", fill='y')
        self.canvas.pack(side='left', fill='both', expand=True)
        self.canvas.create_window((0,0), window=self.master_frame, anchor='nw', tags='self.master_frame')
        self.canvas.config(yscrollcommand=self.vsb.set)
        self.master_frame.grid()

        ###build widgets and place into master_frame
        ...

The master_frame is filled with about 36 widgets placed using the grid geometry manager and reaches a vertical height of about 2000 pixels, but the scrollbar doesn't work.

I saw a post about using ttk scrollbar, but when I imported that I couldn't get it to work. The input statement I used was:

import tkinter as tk
import tkinter.ttk as ttk

and then replaced the line self.vsb = tk.Scrollbar(self.master) with self.vsb = ttk.Scrollbar(self.master) but that didn't fix it either. I also tried removing the min/max sizing on master (those aren't the final values, I've been playing with it).

Is there something I'm doing wrong? I feel like it might be in the line where I set the canvas.config() but I read the documentation and it seems to be right. Tomorrow I plan on trying to load the frame into the canvas after I've built the frame.

But in the meantime, and in case that doesn't work, any help would be great! Thanks!

Solution

You must do three things when configuring a scrolling canvas:

1. have the canvas notify the scrollbar when it scrolls, by configuring the yscrollcommand attribute of the canvas to point to the scrollbar
2. have the scrollbar control the canvas when it is dragged, by configuring the command attribute of the scrollbar
3. tell the canvas what part of the virtual canvas should be scrollable by configuring the scrollregion attribute of the canvas

You are neglecting to do #3. After adding the widgets to master_frame you should do this:

self.canvas.configure(scrollregion=self.canvas.bbox("all")

The above will tell the canvas and scrollbar that the area of the canvas that is scrollable is the area that encompasses all of the objects on the canvas.

Finally, you need to remove the following line of code, because you are already adding the frame to the canvas with create_window. Frames added to a canvas with pack, place or grid won't scroll:

# remove this line
self.master_frame.grid()

For a working example of a scrollable frame, see Adding a scrollbar to a group of widgets in Tkinter

Comments

[Parviz Karimli]

First of all, you shouldn't use both pack and grid geometry managment methods at the same time. Although it doesn't seem the root of the problem, it normally raises a TclError.

[Parviz Karimli]

Secondly, frame widget is used as a container in which other widgets are nested in. So you should have the frame widget: master_frame as the parent of your canvas widget.

[Parviz Karimli]

Thirdly, I also see that you are having some problems with importing and using tkinter properly. Just keep in mind that if you from tkinter import * you can't use tk.<widget>. Otherwise, it will raise a NameError.

[Parviz Karimli]

And you also haven't configured the command option of your scrollbar.

[Parviz Karimli]

Additionally, your scrollbar widget also need to have the frame widget as its parent.

[Russell Smith]

@ParvizKarimli: your comment about master_frame being the parent of the canvas is wrong. It needs to be a child, just as in the question. Also, I see no problem with the imports. Everywhere the OP accesses a Tkinter command, they are prefixing it with tk..

[Djones4822]

I feel like your last bit of code is the most important to me - my master_frame is filled with widgets aligned with the grid() method. When I remove that method, the window shrinks a ton and the scrollbar still doesn't work even after configuring the scrollregion after adding all the widgets

[Djones4822]

I ended up resolving it by using the link you gave and adding the onFrameConfigure function and binding it to the frame's <Configure> but I have no idea why it wouldn't work when I just added the scrollregion line at the end after adding the widgets, any idea there?

[Russell Smith]

@Apc0243: without seeing your code its impossible to know why it didn't work.