starling-handbook-preview

omitted the actual base class: EventDispatcher.
This class equips all display objects with the means to dispatch and handle events. It’s not a
coincidence that all display objects inherit from EventDispatcher; in Starling, the event system is
tightly coupled with the display list. This has some advantages we will see later.
Events are best described by looking at an example.
Imagine for moment that you’ve got a dog; let’s call him Einstein. Several times each day, Einstein
will indicate to you that he wants to go out for a walk. He does so by barking.
class Dog extends Sprite
{
function advanceTime():void
{
if (timeToPee)
{
var event:Event = new Event("bark"); 1
dispatchEvent(event); 2
}
}
}
var einstein:Dog = new Dog();
einstein.addEventListener("bark", onBark); 3
function onBark(event:Event):void 4
{
einstein.walk();
}
1 The string bark will identify the event. It’s encapsulated in an Event instance.
2 Dispatching event will send it to everyone who subscribed to bark events.
3 Here, we do subscribe by calling addEventListener. The first argument is the event type, the
second the listener (a function).
4 When the dog barks, this method will be called with the event as parameter.
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