I have added a toolbar and a button using python add-in assistant (arcmap 10.4). I would like the button to be enable, if and only if, one particular layer (named operations) has exactly one feature selected. I can easily use the __init__ function of the button to test if these circumstances are met at runtime. If they are, the button is enabled, if they are not, the button is disabled. Now, I can't seem to locate any help finding if there is an onUpdate function that can "look" for changes and test to see if the right conditions are met and enable or disable the button appropriately? Is there a listener function/method that I can use to update the button when there are any selection changes that take place within the loaded layer(s)?
