<< Chapter < Page Chapter >> Page >

The addEventListener method in the EventDispatcher class

According to the documentation, the addEventListener method that is defined in the EventDispatcher class " Registers an event listener object with an EventDispatcher object so that the listener receives notification of an event."

Parameters of the addEventListener method

This method requires the following five parameters, the last three of which have default values:

  1. type:String
  2. listener:Function
  3. useCapture:Boolean = false
  4. priority:int = 0
  5. useWeakReference:Boolean = false

Will concentrate on the first two parameters

I will concentrate on the first two parameters in this lesson. In addition, I will refer you to Understanding the AS3 Event Flow by Jody Hall for an excellent discussion of the purpose and use of the third parameter.

The type of the event

The first parameter , which is the type of the event, usually looks something like the following inActionScript syntax:


The event-handler function

The second parameter is the name of a function or method that processes the event. This method must accept an Event object as its only parameter and must return void. A sample ActionScript signature for a suitable event handlermethod follows:

private function activateHandler(event:Event):void

Note that the actual type of the parameter may be any subclass of Event , such as MouseEvent for example. Note also that only the name of the function (without parentheses) is passed to the addEventListener method.

Available to all subclasses of EventDispatcher

The addEventListener method is defined in the EventDispatcher class and inherited by all subclasses of that class. Therefore, the methodcan be called on any object instantiated from any subclass of the EventDispatcher class.

There are many subclasses of the EventDispatcher class

The EventDispatcher class has approximately seventy-five immediate subclasses that ultimately fan out to include hundreds and possibly thousands ofindividual classes. (For example, the Button class is a subclass of the EventDispatcher class about seven levels down the inheritance hierarchy.)

Many combinations are nonsensical

This means that hundreds of different event types can be registered on hundreds of different object types. However, many of those combinations of event types and object types make absolutely no sense at all.

The SolidColor class

For example, one of the subclasses of the EventDispatcher class is named SolidColor . You can register a handler for a MouseEvent.CLICK event on a SolidColor object with no obvious ill effects. There is no compiler error and no runtime error.

However, the registration of the event handler on the object has no effect. As far as I know, it is not possible to cause a SolidColor object to dispatch a CLICK event. Therefore, the click event handler will never be executed.

A weakness in the event model

In my opinion, the ability for the programmer to register event types on objects that will simply ignore events of that type is a major weakness in theActionScript event model. Other programming languages such as Java provide more help in avoiding such programming errors.

Questions & Answers

Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
what school?
biomolecules are e building blocks of every organics and inorganic materials.
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
sciencedirect big data base
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
characteristics of micro business
for teaching engĺish at school how nano technology help us
Do somebody tell me a best nano engineering book for beginners?
s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
what is the actual application of fullerenes nowadays?
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
is Bucky paper clear?
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Do you know which machine is used to that process?
how to fabricate graphene ink ?
for screen printed electrodes ?
What is lattice structure?
s. Reply
of graphene you mean?
or in general
in general
Graphene has a hexagonal structure
On having this app for quite a bit time, Haven't realised there's a chat room in it.
what is biological synthesis of nanoparticles
Sanket Reply
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
Privacy Information Security Software Version 1.1a
Got questions? Join the online conversation and get instant answers!
Jobilize.com Reply

Get the best Algebra and trigonometry course in your pocket!

Source:  OpenStax, Object-oriented programming (oop) with actionscript. OpenStax CNX. Jun 04, 2010 Download for free at http://cnx.org/content/col11202/1.19
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Object-oriented programming (oop) with actionscript' conversation and receive update notifications?