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There are at least three ways to handle event notifications in Flex:

  • Registering an event handler in mxml
  • Creating an inline event handler in the mxml definition
  • Registering an event listener through ActionScript

The XML code in Listing 3 uses the inline approach.

The inline approach

The advantage of using the inline approach, (at least insofar as my Introduction to XML , students are concerned) , is that it doesn't require you to create a Script element within the mxmlor to create a separate ActionScript file.

Handling the slider's change event

Now consider the code that begins with the word change in Listing 3. The code within the quotation marks can be a little hard to explain, but I will give it atry. (The code in quotation marks is actually an ActionScript code fragment.)

Think of it this way

There is a Flex/ActionScript class named Event . The reference to event in Listing 3 is a reference to an object of the Event class that comes into being each time the slider fires a change event .

The Event object encapsulates a property named currentTarget , which is described in the Flex 3 documentation as follows:

"The object that is actively processing the Event object with an event listener. For example, if a user clicks an OK button, the current target couldbe the node containing that button or one of its ancestors that has registered an event listener for that event."

The currentTarget is the slider

In this application, the value of currentTarget points to the slider which is firing change events as the user moves the thumb.

The value property of an HSlider object

The slider is an object of the HSlider class, which has a property named value . The value property contains the current position of the thumb and is a number between the minimum and maximum property values.

Get the current value of the thumb

Therefore, each time the slider fires a change event, the code on the right side of the assignment operator within the highlighted quotation marks inListing 3 gets the numeric value that indicates the current position of the thumb.

Cause the image to be resized

This value is assigned to the height property of the image, causing the overall size of the image to be adjusted, if necessary, to match the currentposition of the slider's thumb. (I could go into more detail as to the sequence of events that causes the size of the image to change, but I will leavethat as an exercise for the student.)

The liveDragging property

That leaves one more attribute or property for us to discuss in Listing 3: liveDragging . This one is much easier to understand.

The Flex 3 documentation has this to say about the liveDragging property:

"Specifies whether live dragging is enabled for the slider. If false, Flex sets the value and values properties and dispatches the change event whenthe user stops dragging the slider thumb. If true, Flex sets the value and values properties and dispatches the change event continuously as the usermoves the thumb. The default value is false."

If liveDragging is false...

If you were to modify the code in Listing 3 to cause the value of the liveDragging property to be false (or simply not set the attribute value to true) , the slider would only fire change events each time the thumb stops moving (as opposed to firing a stream of events while the thumb is moving) . This, in turn, would cause the size of the image to change only when the thumb stops moving instead of changing continuously while the thumb is moving.

Questions & Answers

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
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
Bharti
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
Daniel
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
Maciej
characteristics of micro business
Abigail
for teaching engĺish at school how nano technology help us
Anassong
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
NANO
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
s.
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.
Tarell
what is the actual application of fullerenes nowadays?
Damian
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.
Tarell
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.
Virgil
is Bucky paper clear?
CYNTHIA
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
NANO
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.
Harper
Do you know which machine is used to that process?
s.
how to fabricate graphene ink ?
SUYASH Reply
for screen printed electrodes ?
SUYASH
What is lattice structure?
s. Reply
of graphene you mean?
Ebrahim
or in general
Ebrahim
in general
s.
Graphene has a hexagonal structure
tahir
On having this app for quite a bit time, Haven't realised there's a chat room in it.
Cied
what is biological synthesis of nanoparticles
Sanket Reply
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Source:  OpenStax, Introduction to xml. OpenStax CNX. Dec 02, 2014 Download for free at https://legacy.cnx.org/content/col11207/1.18
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