Tag: actionscript

Using ActionScript Tokenized Asynchronous HTTP Requests

My recent Antarctica Flex/ActionScript app had a requirement for tokenized asynchronous requests. That way I could use a centralized HTTP controller through which every outbound request was submitted. By attaching a “token” to each request, I could properly manage the response payload for the dozen’ish different processes that were going on. In other words, you attach a unique identifier to the outbound request. When the server sends back its response to the client application, this unique identifier is passed along in the payload. Quite cool, right?!

I’ve used this technique in heavy-duty, server-side applications before but only a few times in a web client. In practice it works brilliantly and it allowed me to easily organize the HTTP responses from many different types of requests and keep them all straight. At the heart of controller was this pseudo-code. If you haven’t done this before, there are just a few tricks to make it work right. I’ve included all the code to make your life easier. The token variable is a String that you create and then pass to the AsynchResponder.

                               
_http = new HTTPService();
_http.concurrency = "multiple";
_http.requestTimeout = 20;
_http.method = "POST";

var asyncToken:AsyncToken = _http.send( paramsObject );  
                                     
//you pass the token variable in as a String
var token:String = "someValue";
var responder:AsyncResponder = new AsyncResponder(resultHandler,faultHandler,token);
asyncToken.addResponder(responder);

Elsewhere in the app, the other classes that used the controller received the response payload via the event bus and then filtered the response by the tokens using a switch/case statement. AppEvent is my custom event bus that would broadcast the payload to the entire application via an Event. This allowed me to fully decouple the http controller from being directly wired into my other classes. It made the app very flexible in that action would only be taken when the response came back. If you want a few more details about this architecture, then check out my blog post on it. Here’s the HTTP response handler pseudo-code that is inside the controller.

Just a note, the HTTPData Class is a custom object I wrote to manage the response data. You could manage the data anyway you like. This is just one example of how to do it.

private function resultHandler(result:Object, token:Object = null):void
{	
	var httpData:HTTPData = new HTTPData();
	httpData.result = result.result;
	httpData.token = token; 
	AppEvent.dispatch(AppEvent.HTTP_RESULT,httpData);
}

And, here’s the response handler that’s inside one of the applications pages (views) that recieve the payload via my event bus:

AppEvent.addListener(AppEvent.HTTP_RESULT,httpResultHandler);

/**
 * Handles setting up many of the user variables based on tokenized,
 * asynchronous HTTP requests.
 * @param event AppEvent from HTTP request.
 */
private function httpResultHandler(event:AppEvent):void
{
    var json:String = event.data.result as String;	
    
    //route the tokens through a switch/case statement
    switch(event.data.token)
    {
         case "getallgpspoints":
              parseGPSPoints2(json);
              break;
    }
}

You can download the entire controller example here. If you use it for your own work, you’ll have to comment out anything you don’t need like some of the import statements and the custom events. Have fun!

Figuring out Date Time Zones in Adobe Flex/Actionscript

I was really frustrated the past few weeks when a major clock component of an app kept failing when viewed from different time zones. It was always supposed to show Antarctica time and only that. I searched and searched for definitive examples on the web, but never found what I needed.

At the heart of this is the ActionScript Date Class. It’s unfortunately a very poor implementation. I expected to simply have a property where you give the Class a timezone offset and presto you magically get the time for that location of the world. Silly me. In addition the documentation is incorrect in that the getTime() method does NOT in fact report the time in UTC. And, to make things even more fun, the getTimeZoneOffset() method returns minutes rather than milliseconds.

However, after enough iterations I was finally able to cobble together what seems to be a graceful solution. The trick is to use the getTime() method. Then add the time zone offset in milliseconds. This, in theory, gives you UTC time. Then add or subtract the number of hours in milliseconds for your fixed clock. Oh, and I also used the DateTimeFormatter to beautify everything up. Here’s the code to hopefully save someone else a bunch of additional coding:

var df:DateTimeFormatter = new DateTimeFormatter();
df.useUTC = false;
df.timeStyle = "short";
df.dateStyle = "medium";
var d:Date = new Date();

var millisecondsPerThreeHours:int = 1000 * 60 * 60 * 3; //using a -3 hour UTC offset
var timeZoneOffsetMilliSeconds:Number = d.getTimezoneOffset() * 60 * 1000;

d.setTime(d.getTime() + timeZoneOffsetMilliSeconds - millisecondsPerThreeHours);

var antarcticaTime2:String = d.toString();
antarcticaTimeTextArea.text = df.format(antarcticaTime2);

Live From Antarctica – the final 7th Summit.

Our team just finished a massive 5 weeks push to building an app for the Romero family, and in particular Jordan, to follow him on his climb of the final summit on the continent at the bottom of the world. You can find the app on his home page today https://jordanromero.com, or access it directly here https://edn1.esri.com/antarctica.

It was actually Jordan’s dream to climb the highest summits on the major continents. And, he is now on his way to accomplish all that…and before his 16th birthday during what is considered summer in Antarctica. I’m amazed at what he has done. I can’t help but think about what he might be able to accomplish in the future now that he has accomplished a feat that very few ever do.

The app is capturing live GPS coordinates (altitude, heading, speed, lat/lon), live weather and it also includes a Challenge component that anyone can take to conquer their own 7 summits on their own time by walking, swimming, running or biking.

I encourage you to check out the app and even take the Challenge!

For the techno-geeks reading this, here is some background info on the technology. GPS processing and ArcGIS mapping backend services were built in C#.NET by AL Laframboise. The Challenge service and REST endpoints were built in C#.NET by Nick Furness. I built the the Adobe Flex/ActionScript client application using Adobe FlashBuilder 4.5, and the ArcGIS API for Flex provided the client-side mapping. The look and feel were accomplished by the excellent help of UX engineer Frank Garofalo in Esri Professional Services. The client app uses a custom dependency injection model at the core, and the skins were built using Adobe Catalyst.