User Guide

Using the ExternalInterface class 505

If the container is an HTML page, this method invokes the JavaScript function with the

specified name, which must be defined in a

page. The return value of the JavaScript function is passed back to ActionScript.

// 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” on page 522.

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