How to invoke an ActionScript method from JavaScript (HTMLLoader) object in AIR?

Question

So I have an Application Sandbox HTMLLoader object which I create in AIR and simply want to call ActionScript methods from JavaScript. In Flash, this is accomplished through our trusty ExternalInterface.addCallback() function. However in AIR, things are quite a bit different, and I just can't seem to get it to work.

Here is a simplified overview of my project:

My AIR (ActionScript) main:

public class Main extends Sprite {

    public var _as3Var:String = "testing";
    public function as3Function():void
    {
        trace("as3Function called from Javascript");
    }

    public function Main() {
        NativeApplication.nativeApplication.addEventListener(InvokeEvent.INVOKE, onInvoke);
    }

    protected function onInvoke(e:InvokeEvent):void {
        NativeApplication.nativeApplication.removeEventListener(InvokeEvent.INVOKE, onInvoke );
        var app = new App();
        addChild(app);
        app.init(new ExternalContainer(), e.currentDirectory, e.arguments);
    }
}

And this is how I create my HTMLLoader object:

{
    _html = new HTMLLoader();
    _html.useCache = false;
    _html.runtimeApplicationDomain = ApplicationDomain.currentDomain;
    _html.load(new URLRequest("sandbox/AirRoot.html"));
    _html.width = 800;
    _html.height = 600;
    App.ref.addChild(_html);
}

And at last, here is my snippet of JavaScript in my AirRoot.html file which is trying to call the public method as3Function() declared in my Main class:

Exposed.testAs3 = function()
{
    air.trace("Exposed.testAs3 called");            /* This works fine. */
    air.trace("runtimeVersion:");                   /* This works fine. */
    air.trace(air.NativeApplication.nativeApplication.runtimeVersion);  /* This works fine. */
    air.trace("seeing if I can get to AS3 params...");  /* This works fine. */

    /* This doesn't work - get the following error: TypeError: Value undefined does not allow function calls. */
    air.NativeApplication.nativeApplication.as3Function();
}

What am I missing?

Answer 1

OK, I am going to answer my own question. I promise this was not a ploy to gain more reputation points, but I was seriously confused today but have now found the appropriate answers and documentation - which is usually the main problem to many an engineer's question...

Anyway, the answer:

The AIR HTMLLoader object contains a magical property, HTMLLoader.window, which is a proxy to the JavaScript window object. So setting HTMLLoader.window = AS3Function; is one way - or in relation to my previously included example (assuming I setup a static property called Main which pointed to the Main class):

_html.window.as3Function = Main.as3Function;

And now in JavaScript I can just call as3Function as:

<script>
    window.as3Function();
</script>

Another interesting property is the JavaScript "window.htmlLoader" object. It is a proxy to the AS3 HTMLLoader parent object, in my case, the _html object. From this you can access things in relation to the _html object from JavaScript.

Answer 2

I'm not sure if this is a change in the new version of AIR, but you no longer need to reference the window in the javascript call, you can just do this:

as3Function();