Learning MIT App Inventor: A Hands-On Guide to Building Your Own Android Apps

The Basics

A list is multiple pieces of data stuck together, one after another. Those pieces of data are in order, meaning that whatever is in slot 1 of the list will stay there unless you move it. Every item in the list has a number, starting with 1. Figure 6.3 shows what lists look like to the phone. Each cell is a place you can put something (a number, a piece of text, or anything else), and each something has a number. There are no empty items: Each item has to have something in it, and no numbers are skipped.

Figure 6.3 What a list looks like in the phone’s memory.

The list itself is a container. Regardless of how much stuff is inside ...