I've got an activity that only opens via a notification. That notification can pop up while in the activity as well. Is there a way to tell the notification the activity is already open so I can change its behavior accordingly?
There is no way for the notification to know, it just has a
PendingIntent that is fired when it's clicked. But you can be smart about handling the intent.
For your case I think you should look at Activity launch modes. Specifically I think adding
launchMode="singleTop" to your
<activity> tag in
AndroidManifest.xml does exactly what you want.