MACROMEDIA FLEX-GETTING STARTED WITH FLEX Getting Started page 17

The second line begins with the
This tag includes the Flex namespace declaration. The content between the beginning and end
<mx:Application>
As it is written, this example lays out the user interface, but does not yet contain the application
logic to copy the input text from the TextInput control to the TextArea control. The next section
adds that logic.
Adding ActionScript to a Flex Application
ActionScript follows the ECMA-262 Standard Edition 4 (the specification written by the
European Computer Manufacturers Association) unless otherwise noted. For more information
on ActionScript, see
You can use ActionScript for the following purposes:
Handling events
Button control, the Button generates an event. You handle events by defining functions in
ActionScript. Your event handler could open a window, play a SWF file, or perform whatever
action is necessary for your application.
Handling errors You handle runtime errors in ActionScript. You can detect data validation
errors and signal the error to the user, resubmit a request to the server, or perform some other
actions based on your application.
Binding data objects to a
to populate a data model from a Flex control, or populate a control from a data model.
Defining custom components
class hierarchy to create components specific to your application requirements.
The following example is a modification to the example in the previous section that adds an event
handler for the
click
executed in response to a user action. The event handler in this example copies the text from the
TextInput control to the TextArea control when the user selects the Button control:
<?xml version="1.0"?>
<!-- ?xml tag must start in line 1 column 1 -->
<!-- MXML root element tag. -->
<mx:Application xmlns:mx="http://www.macromedia.com/2003/mxml" >
<!-- Flex controls exist in a container. Define a Panel container. -->
<mx:Panel title="My Application">
<!-- TextInput control for user input. -->
<mx:TextInput id="myInput" width="150" text=""
<!-- Button control that triggers the copy. -->
<mx:Button id="myButton" label="Copy Text"
click="myText.text=myInput.text;" />
<!-- Output TextArea control. -->
<mx:TextArea id="myText" text="" width="150" />
<mx:Application>
tags defines the Flex application.
Chapter 3, "Using ActionScript," on page
The Flex user interface is event-driven. For example, when a user selects a
Flex control within an MXML statement
You can derive custom components from the Flex component
event of the Button control. An event handler is ActionScript code that is
tag, the root element of a Flex application.
43.
You can use data binding
/>
The Flex programming model 17