屏幕截图不在facebook钛中分享

Question

 var media;
    Titanium.Media.takeScreenshot(function(e) {
     media=e.media;       
           }
        );


        var data = {
        link: "https://developer.mozilla.org/en/JavaScript",
        name: "Best online Javascript reference",
        message: " Javascript reference",
        caption: "Timbodi",
        picture: media,
        description: "This section of the site is dedicated to JavaScript-the-language, the parts that are not specific to web pages or other host environments...",
        test: [ {foo:'Encoding test', bar:'Durp durp'}, 'test' ]
    };
    facebook.requestWithGraphPath('me/feed', data, 'POST', showRequestResult);

分享屏幕截图，但在facebook中显示的图像是不同的。 请帮助我是钛的新手。