Using ExternalInterface in Flash

Question

I'm trying to edit some flash to make an external javascript function call, but with no success. Here's my actionscript 2.0 code:

//testing external .js calls

import flash.external.ExternalInterface;

//attempting to make external js call

ExternalInterface.call("createPlaylist","It's my Life!");

and here's my javascript;

function createPlaylist(mess){
  alert("called createPlaylist: " + mess);
}

I've seen lots of examples and I'm mainly confused about the use of ExternalInterface.addCallback. I don't need the javascript to return anything to flash, so is this necessary?

For whatever reason, I never see the alert. Does anyone see any problems in my code? Is there some ExternalInterface library I don't have? Also, what's the BEST way to use ExternalInterface (ie; error checking, etc.) Thanks in advance...

Answer 1

ExternalInterface.addCallback is for javascript to be able to call into your Flash application. If for example you want a HTML button that starts/stops a video you just add a callback for a named method and your js can than call [FlashObject].callback method name.

I would say that the best way to add ExternalInterface methods in your application is to set up a class responsible for JS communication for each interaction case in the app. For example:

public class ExternalVideoControl {

    private var video:MediaDisplay;

    public function ExternalVideoControl(video:MediaDisplay) {
        //ExternalInterface.addCallback  - one callback for each method you want to expose, pointing to a method within this class;
        //add listeners on the video player and point them to methods in this class, for example onProgress
    }
    public function playVideo():void {
        //play the video on the mediaDisplay
    }
    private function onProgress(event:ProgressEvent):void {
        //ExternalInterface.call - report progress back to javascript
    }
}

To test ExternalInterface more directly, try calling

ExternalInterface.call("alert", "Hello World!");