Here's a workaround: you can navigate to the sharing URL from Flash, loaded with the appropriate parameters and opening it on a new window. The following function should work for this purpose:
import flash.net.*;
/**
* Function that allows sharing a page in Facebook
* @param sharedTitle String with the title of the page that you want to share in Facebook
* @param sharedURL String with the full URL that you want to share in Facebook
* @param sharedSummary (Optional) String with a description about your shared content
* @param sharedImageURL (Optional) String with the full URL where the image to display next to your shared post is located
*/
function shareInFacebook(sharedTitle : String, sharedURL : String, sharedSummary : String = null, sharedImageURL : String = null) : void {
var fullURLString = "";
fullURLString += "http://www.facebook.com/sharer.php?s=100";
fullURLString += "&p[title]=" + encodeURIComponent(sharedTitle);
fullURLString += "&p[url]=" + encodeURIComponent(sharedURL);
if (sharedImageURL != null) {
fullURLString += "&p[images][0]=" + encodeURIComponent(sharedImageURL);
}
if (sharedSummary != null) {
fullURLString += "&p[summary]=" + encodeURIComponent(sharedSummary);
}
var theRequest : URLRequest = new URLRequest(fullURLString);
navigateToURL(theRequest, "_blank");
}
Call this function when a button is clicked and you should get a custom Facebook button inside Flash.
More information about how to build a URL to share in Facebook with all parameters (that you can call via Flash:)
Facebook Share doesn't show my description or my thumbnail
And more here as well, including the meta-tags that you can put into your embedding HTML:
How do I customize Facebook's sharer.php