How do you implement the “Up” navigation button in Android 4.0?

[bosss]

I'm in the process of teaching myself how to build Android apps by building a simple chat app. I have an Android phone, which is rooted and currently on the latest version of Android (4.0.4 Ice Cream Sandwich, as of this writing). I've been pouring over the Android Dev Guide and Android Design websites frantically, absorbing as much information as I possibly can. It's been pretty beneficial!One thing that has been talked about a lot is the introduction of the "Up" navigation button in Android. While I don't see the real purpose in it, it would be a good learning experience for me on how to implement it. The question is: how do I implement it? I get the feeling that I could use my app's icon, plus a little grey left-facing arrow to signify back. My problem is that I have no idea how to capture that input and create an intent to go back. Is it the same as capturing any other user input and building a listener object from there? Or do I have to build something a bit more complex? Any and all help would be very helpful, and if my question wasn't clear, I'll be happy to reword my question if necessary.