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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:

Event.ACTIVATE

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

Application of nanotechnology in medicine
what is variations in raman spectra for nanomaterials
Jyoti Reply
I only see partial conversation and what's the question here!
Crow Reply
what about nanotechnology for water purification
RAW Reply
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
Damian
yes that's correct
Professor
I think
Professor
what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
Rafiq
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
Damian
How we are making nano material?
LITNING Reply
what is a peer
LITNING Reply
What is meant by 'nano scale'?
LITNING Reply
What is STMs full form?
LITNING
scanning tunneling microscope
Sahil
how nano science is used for hydrophobicity
Santosh
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
Rafiq
what is differents between GO and RGO?
Mahi
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
Rafiq
if virus is killing to make ARTIFICIAL DNA OF GRAPHENE FOR KILLED THE VIRUS .THIS IS OUR ASSUMPTION
Anam
analytical skills graphene is prepared to kill any type viruses .
Anam
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
Bob
The nanotechnology is as new science, to scale nanometric
brayan
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Damian
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
Renato
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
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
Adin
why?
Adin
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
research.net
kanaga
sciencedirect big data base
Ernesto
Introduction about quantum dots in nanotechnology
Praveena Reply
hi
Loga
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
Bharti
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, Object-oriented programming (oop) with actionscript. OpenStax CNX. Jun 04, 2010 Download for free at http://cnx.org/content/col11202/1.19
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