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

Component Properties: The Built-in Variables

You have already seen that each component you have in your app has some collection of properties that are visible in the Designer screen. These properties control various traits of that particular component, including its color, the text it displays, and its shape, among many others. Each component has a set of parameters that are relevant to that type of component. A check box has the property isChecked, which describes, as you may guess, whether that check box is currently checked. No other component has the concept of being checked, so no other component has this property. But the check box does display some text, so it also has a text property, as do many other components.

All the properties you ...