1. Flex Training Day 4:
Flex Events, Metadata & View States

2.  What are Events?
 Events propagation in Flex
 Custom Events
 Metadata tags
 View States in Flex

3.  Events let us know when something happens
within an application
 Any user or system interaction with your
application can generate events
 Components generate and dispatch events
and consume (listen to) other events.

4.  An event system consists of 3 main
entities: dispatchers, listeners, and event
objects. Event dispatchers are objects that
dispatch events to objects that are registered
as listeners

5.  Almost all event classes extend the
flash.events.Event class
 EventDispatcher gives the classes a capability
to participate fully in the event model.
 All DisplayList items extend from
EventDispatcher
 For non-visual components we can also
implement the IEventDispatcher interface

6. When events are triggered, there are
three phases in which Flex checks
whether there are event listeners.
These phases occur in the following
order:
•Capturing
•Targeting
•Bubbling
‘target’ property refers to the
dispatcher of the event.
The ’currentTarget’ property refers to
the current node that is being
examined for event listeners.

7.  During any phase, you can stop the traversal of the
display list by calling one of the following methods
on the Event object:
 stopPropagation()
 stopImmediatePropagation()
Both methods prevents the Event
object from moving on to the next node,
With the difference that stopImmediatePropagation
() does not allow any other event listeners on the
current node to execute

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9.  Metadata tag is the information
to the Flex compiler that
describes how components are
used in a Flex application
 The metadata tags define
component attributes, data
binding properties, events, and
other properties of the
component. Flex interprets
these statements during
compilation; they are never
interpreted during run time.
 Metadata statements are
associated with a class
declaration, an individual data
field, or a method.
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11.  What are view states?
In many rich Internet
applications, the
interface changes based
on the task the user is
performing. A simple
example is an image that
changes when the user
rolls the mouse over it.
View states let you A.Default view state B.Rich view state
easily implement such
applications.

12. A.Modified title of Panel container B.New form item C.Modified label of Button control D.New LinkButton control
•Item Creation Policy – deferred or immediate