Error Handling when File/URL not found

Question

I am paging through a list of items in a datagrid and calling
a URL (actually a local file) based upon which item in the grid was
clicked. I'd like to throw an error if the file does not exist, but
I can't figure out how. Can some one give me a clue? The docs on
this subject are confusing to me. Here is the code:
//add the search function for when the button is pressed
import fl.controls.DataGrid;
import fl.data.DataProvider;
import fl.events.ListEvent;
import flash.display.Sprite;
getAcrobat.addEventListener(MouseEvent.CLICK,acroReader);
backButton.addEventListener(MouseEvent.CLICK,goBack);
litGrid.addEventListener(ListEvent.ITEM_CLICK,showPDF);
function acroReader(e:MouseEvent) {
var urlAcro:String = "
http://www.adobe.com/products/acrobat/readstep2.html";
var request:URLRequest = new URLRequest(urlAcro);
try {
navigateToURL(request, '_blank');// second argument is
target
} catch (e:Error) {
trace("Page was not found!");
function goBack(e:MouseEvent) {
gotoAndPlay(1,"Scene 1");
var XMLLiterature:XML = new XML();
var XMLLit:URLRequest = new URLRequest("literature.xml");
var XMLLoad:URLLoader = new URLLoader(XMLLit);
var urlArray:Array = new Array();
var theSelection:int = 0;
XMLLoad.addEventListener(Event.COMPLETE,loadLit);
function loadLit(e:Event):void {
XMLLiterature = new XML(e.target.data);
for each (var item in XMLLiterature.lit) {
var litTitle = item.litTitle;
var url = item.fileName;
//var fileName = item.fileName;
litGrid.addItem({AvailableLiterature:litTitle});
//urlArray.push({Title:litTitle,url:url});
function showPDF(e:ListEvent):void {
var theSelection = e.rowIndex;
var theRequest =
"pdf/"+XMLLiterature.lit.fileName[theSelection];
var theLitRequest:URLRequest = new URLRequest(theRequest);
try {
navigateToURL(theLitRequest, '_blank');// second argument is
target
} catch (err:Error) {
trace("Page was not found!");
stop();

Answer 1

When you setup your URLLoader, also listen for an
IOErrorEvent, which will fire if the file does not exist. Here is
an example:
package {
import flash.display.Sprite;
import flash.events.IOErrorEvent;
import flash.net.URLLoader;
import flash.net.URLRequest;
public class IOErrorEventExample extends Sprite {
public function IOErrorEventExample() {
var loader:URLLoader = new URLLoader();
loader.addEventListener(IOErrorEvent.IO_ERROR,
ioErrorHandler);
var request:URLRequest = new URLRequest("MissingFile.xml");
loader.load(request);
private function ioErrorHandler(event:IOErrorEvent):void {
trace("ioErrorHandler: " + event);
}