MACROMEDIA COLDFUSION MX 7.0.2-USING COLDFUSION MX WITH FLEX 2 Guia do Utilizador descarregar pdf (Página 146)

146 Use an Event Listener

11. Switch to Source mode and examine the code generated by Flex Builder.

Your code should look as follows (your coordinate values may vary):

<?xml version="1.0" encoding="utf-8"?>

<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml"

layout="absolute">

<mx:Panel x="20" y="20" width="450" height="150" layout="absolute"

title="Currency Converter">

<mx:Label x="25" y="37" text="Price in Dollars"/>

<mx:Label x="120" y="65" id="lblResults"/>

<mx:TextInput x="120" y="35" id="txtPrice"/>

<mx:Button x="290" y="35" label="Convert to Yen" id="btnConvert"/

</mx:Panel>

</mx:Application>

12.

Save your file.

Write an event listener

Next, you write an event listener for the Convert to Yen button. You want the listener to

consist of an ActionScript function that can calculate and display a specified dollar price in

yen.

1. Switch to Source mode and place the insertion point immediately after the opening

<mx:Application> tag.

2. Start typing <mx:Script> until the full tag is selected in the code hints, press Enter to insert

the tag in your code, and then type the closing angle bracket (>) to complete the tag.

Flex Builder enters an

<mx:Script> script block that also includes a CDATA construct.

3. Enter or paste the following code in the CDATA construct:

public function convertCurrency():void {

var rate:Number = 120;

var price:Number = Number(txtPrice.text);

if (isNaN(price)) {

lblResults.text = "Please enter a valid price.";

} else {

price = price * rate;

lblResults.text = "Price in Yen: " + String(price);

}

NOTE

When using an <mx:Script> script block, you should wrap the contents in a CDATA

construct. This prevents the compiler from interpreting the contents of the script

block as XML, and allows the ActionScript to be properly generated.

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MACROMEDIA COLDFUSION MX 7.0.2-USING COLDFUSION MX WITH FLEX 2 Guia do Utilizador Página 146