as3 loop loading urls - continue loop on complete - actionscript-3

Question

I am trying to load a bunch of files in order. I want the other to start downloading once the previous has downloaded. I thought the best way to do this would be thru a for loop.
TheURL = is a bunch of urls in a ARRAY
for(var i:int=0;i<TheURL.length;i++)
{
var urlString:String = TheURL[i];
var urlReq:URLRequest = new URLRequest(urlString);
var urlStream:URLStream = new URLStream();
var fileData:ByteArray = new ByteArray();
urlStream.addEventListener(Event.COMPLETE, loaded);
urlStream.load(urlReq);
function loaded(event:Event):void
{
/// code to continue loop
}
}
It is important that the others do not start downloading until the previous has completed. Any suggestions on how to do that? Thanks

Answer 1

function downloadFiles():void
{
downloadNextFile();
}
function downloadNextFile():void
{
var urlString:String = TheURL.shift();
var urlReq:URLRequest = new URLRequest(urlString);
var urlStream:URLStream = new URLStream();
var fileData:ByteArray = new ByteArray();
urlStream.addEventListener(Event.COMPLETE, loaded);
urlStream.load(urlReq);
}
function loaded(event:Event):void
{
downloadNextFile();
}

Answer 2

Using a for-loop does not solve what you want to do.
In my opinion the easiest way should be to use the array of URLs as a queue. This can be done by using Array.shift(). But you should make a copy of your array if you need the original set of URLs when finished, because shift() makes an inline modification of the array.
The solution could be the following:
function loadQueue(urlQueue:Array):void
{
var url:String = urlQueue.shift();
var request:URLRequest = new URLRequest(url);
var stream:URLStream = new URLStream();
var data:ByteArray = new ByteArray();
var completeHandler:Function = function(event:Event)
{
// remove listener from stream to be a clean coder ;)
stream.removeEventListener(Event.COMPLETE, completeHandler);
// handle completion in the way you need ...
// continue with the next element
if (urlQueue.length > 0)
loadQueue(urls);
}
urlStream.addEventListener(Event.COMPLETE, loaded);
urlStream.load(urlReq);
}
Loading your queue will then look like:
loadQueue(TheURL.concat()); // concat() will clone your array

Answer 3

You should use a library like greensock LoaderMax http://www.greensock.com/loadermax/.
It's much more difficult than it seems to create your own loading queue. There are plenty of bugs, traps and special cases to deal with. It seems to work fine, and one day a customer call you back because of a bug on this particular flash version on this computer behind this firewall... I've started to do mine library, but finally I used LoadManager.