How to bind events to Canvas items?

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Question :

How to bind events to Canvas items?

If I’m using a canvas to display data and I want the user to be able to click on various items on the canvas in order to get more information or interact with it in some way, what’s the best way of going about this?

Searching online I can find information about how to bind events to tags but that seems to be more indirect then what I want. I don’t want to group items with tags, but rather have specific function calls when the user clicks specific items on the canvas.

Asked By: Ian


Answer #1:

To interact with objects contained in a Canvas object you need to use tag_bind() which has this format: tag_bind(item, event=None, callback=None, add=None)

The item parameter can be either a tag or an id.

Here is an example to illustrate the concept:

from tkinter import * 

def onObjectClick(event):                  
    print('Got object click', event.x, event.y)
    print(event.widget.find_closest(event.x, event.y))

root = Tk()
canv = Canvas(root, width=100, height=100)
obj1Id = canv.create_line(0, 30, 100, 30, width=5, tags="obj1Tag")
obj2Id = canv.create_text(50, 70, text='Click', tags='obj2Tag')

canv.tag_bind(obj1Id, '<ButtonPress-1>', onObjectClick)       
canv.tag_bind('obj2Tag', '<ButtonPress-1>', onObjectClick)   
print('obj1Id: ', obj1Id)
print('obj2Id: ', obj2Id)
Answered By: tdedecko

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