External Interface

ExternalInterface is a class in the flash.external package that enables communication between ActionScript and the Flash Player container (e.g. an HTML page with JavaScript).

ExternalInterface is especially useful for two-way Flex application and browser JavaScript integration. In fact, Adobe recommends using ExternalInterface for all ActionScript-JavaScript communication.

ExternalInterface exposes two key pieces of functionality:

addCallback( functionName:String, closure:Function ) - expose a Flex function to the container

• calling a container function (calling JavaScript from ActionScript)
• exposing a Flex function to be callable by the container (calling ActionScript from JavaScript)
• Example:

• ExternalInterface.addCallback("sendToActionScript", receivedFromJavaScript);
• "sendToActionScript" is defined in JS, receivedFromJavaScript is defined in AS.

ExternalInterface defines two especially important static functions:

• call( functionName:String, ... arguments ) - call a container function
• 
  

ExternalInterface.call("sendToJavaScript", input.text);

Flex and JavaScript Integration

Use the ExternalInterface class for ActionScript-JavaScript communication.

ExternalInterface defines two especially important static functions:

• call( functionName:String, ... arguments ) - call a container function
• addCallback( functionName:String, closure:Function ) - expose a Flex function to the container

Examples

Call Browser/JavaScript from ActionScript

Calling JavaScript from ActionScript is easy with ExternalInterface . Simply call the static call()function passing the function name and, optionally, any arguments.

// call a JavaScript function defined in the container page
   var result:String = 
      ExternalInterface.call( "doSomethingInJavaScript", arg1, arg2 );

The above ActionScript code could call the below JavaScript code in the container HTML page:

// a JavaScript function in the container HTML page
   function doSomethingInJavaScript( arg1, arg2 )
   {
      // do something
      return "results for " + arg1 + " and " + arg2;
   }

Call ActionScript from JavaScript/Browser

Calling ActionScript from JavaScript again requires use of the ExternalInterface class. First we must use the addCallback() function to expose the ActionScript function we want to call to the container.

public function init():void
   {
      // expose an ActionScript function to the container
      ExternalInterface.addCallback( "doSomethingInActionScript", doSomethingInActionScript );
   }
   
   // function now callable from JavaScript
   public function doSomethingInActionScript( arg1:String, arg2:Number ):String
   {
      return "result";
   }

The below JavaScript code can be used to call the exposed ActionScript function:

// get the Flex application (Flash object)
   var isIE = navigator.appName.indexOf("Microsoft") != -1;
   var flashName = "flashObjectName";
   var flashObject = (isIE) ? parent.Main.window[flashName] : document[flashName];
   
   if( flashObject )
   {
      // call the Flex application (Flash object)
      flashObject.doSomethingInActionScript( "arg1", 2 );
   }

Make sure the Flex application has been initialized and the function callback has been registered beforethe JavaScript call.