ActionScript™ 3.0 Bible

Chapter 16. Understanding Events

Introduction

In this chapter

• Learning about the new event framework in AS3

• Understanding the basics of event objects and event dispatchers

• Understanding the Display List's event flow

ActionScript 3.0 adds a powerful framework for handling internal communication known as the event framework. Events are messages that are sent between objects when an action, such as a button click, has taken place. This enables you to create functionality that occurs sequentially without the need for the Flash Timeline or for complicated method calls to other classes.

The Flash Player 9 API uses events for many different purposes that were formerly handled in loose and inconsistent ways. Mouse actions, timers, networking, and asynchronous errors are all examples. We'll talk about how these subsystems use the event framework.

We'll take a look at how EventDispatcher objects communicate and the structure of the new Event objects. We'll also look at some of the more advanced features of the event framework, including how to create your own custom events and how to use the new event bubbling feature.

Introducing Events

What exactly is an event? At its core, an event is an object that represents an occurrence and describes the conditions surrounding that occurrence, including but not limited to, a description of the event, called the event type, and the origin of the event, also known as the event target.

This is by no means a new concept. In the past, ActionScript users have had ...