Calling external code from ActionScript -- Flash CS3

The ExternalInterface.call() method executes code in the container application. It requires at least one parameter, a string containing the name of the function to be called in the container application. Any additional parameters passed to the ExternalInterface.call() method are passed along to the container as parameters of the function call.

// calls the external function "addNumbers"
// passing two parameters, and assigning that function's result
// to the variable "result"
var param1:uint = 3;
var param2:uint = 7;
var result:uint = ExternalInterface.call("addNumbers", param1, param2);

If the container is an HTML page, this method invokes the JavaScript function with the specified name, which must be defined in a script element in the containing HTML page. The return value of the JavaScript function is passed back to ActionScript.

<script language="JavaScript">
    // adds two numbers, and sends the result back to ActionScript
    function addNumbers(num1, num2)
    {
        return (num1 + num2);
    }
</script>

If the container is some other ActiveX container, this method causes the Flash Player ActiveX control to dispatch its FlashCall event. The specified function name and any parameters are serialized into an XML string by Flash Player. The container can access that information in the request property of the event object and use it to determine how to execute its own code. To return a value to ActionScript, the container code calls the ActiveX object's SetReturnValue() method, passing the result (serialized into an XML string) as a parameter of that method. For more information about the XML format used for this communication, see The external API's XML format.

Whether the container is a web browser or another ActiveX container, if the call fails or the container method does not specify a return value, null is returned. The ExternalInterface.call() method throws a SecurityError exception if the containing environment belongs to a security sandbox to which the calling code does not have access. You can work around this by setting an appropriate value for allowScriptAccess in the containing environment. For example, to change the value of allowScriptAccess in an HTML page, you would edit the appropriate attribute in the object and embed tags.