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App Inventor 2, 2nd Edition
book

App Inventor 2, 2nd Edition

by David Wolber, Hal Abelson, Ellen Spertus, Liz Looney
October 2014
Beginner to intermediate content levelBeginner to intermediate
360 pages
9h 3m
English
O'Reilly Media, Inc.
Content preview from App Inventor 2, 2nd Edition

Chapter 14. Understanding an App’s Architecture

Figure 14-0.
Understanding an app

This chapter examines the structure of an app from a programmer’s perspective. It begins with the traditional analogy that an app is like a recipe and then proceeds to reconceptualize an app as a set of components that respond to events. The chapter also examines how apps can ask questions, repeat, remember, and talk to the Web, all of which will be described in more detail in later chapters.

Many people can tell you what an app is from a user’s perspective, but understanding what it is from a programmer’s perspective is more complicated. Apps have an internal structure that you must understand in order to create them effectively.

One way to describe an app’s internals is to break it into two parts, its components and its behaviors. Roughly, these correspond to the two main windows you use in App Inventor: you use the Component Designer to specify the objects (components) of the app, and you use the Blocks Editor to program how the app responds to the user and external events (the app’s behavior).

Figure 14-1 provides an overview of this app architecture. In this chapter, we’ll explore this architecture in detail.

Alt Text
Figure 14-1. The internal architecture of an App Inventor app

Components

There are two main types of components ...

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Publisher Resources

ISBN: 9781491907214Errata Page