Have Combobox Listen to AddLayer Event?

[MikeMacRae]

I am building an addin combobox. The combobox will populate a list of all the layers that are in the TOC in ArcMap upon initialization of ArcMap. The user will choose a layer and some actions will take place.

What I want to do is have the comobox listen to the Table of Contents and update any time the user adds or removes a layer automatically. Is this possible?

Thanks

[FreddieGibson · Accepted solution]

You would need to implement both the ComboBox and an Application Extension. The Application Extension would need to listen for changes in the TOC and you'd need to build a hook to feed the values to the ComboBox. I haven't tested it, but I'm thinking it'd look something like this.

import arcpy
import pythonaddins

class ComboBoxClass(object):
    """Implementation for ComboBox"""
    def __init__(self):
        self.items = list()
        self.editable = self.enabled = True
        self.dropdownWidth = self.width = 'WWWWWW'
        ComboBoxClass._hook = self        

class ExtensionClass(object):
    """Implementation for Application Extension """
    def __init__(self):
        self.enabled = True
        ExtensionClass._hook = self
        
    def itemAdded(self, new_item):
        ComboBoxClass._hook.items.extend([new_item])
        
    def itemDeleted(self, deleted_item):
        ComboBoxClass._hook.items.remove(deleted_item)    

[MikeMacRae]

HeyFreddie. You have me chasing down a better understanding of hooking in python. I've used your example and modified it a bit. This worked well. Thanks for the input.