Android Programming: The Big Nerd Ranch Guide

Tasks and the Back Stack

Android uses tasks to keep track of the user’s state within each running application. A task is a stack of activities that the user is concerned with. The activity at the bottom of the stack is called the base activity, and whatever activity is on top is the activity that the user sees. When you press the Back button, you are popping the top activity off of this stack. If you are looking at the base activity and hit the Back button, it will send you to the home screen.

Using the task manager, you can switch between tasks without affecting each task’s state. For instance, if you start entering a new contact and switch to checking your Twitter feed, you will have two tasks started. If you switch back to editing contacts, ...