父页面操作子页面的dom,通过子页面的URL怎么做

    appcan.ready(function() {
            titHeight = $('#header').offset().height;
            content = $('#reply').offset().height;
            var url = "http://192.168.1.195/jc6/wfAndroidHtml/knowledge2.html?UserCode=xiaoyujie%24356a192b7913b04c54574d18c28d46e6395428ab&AppTID=ff8080814a98d7af014a99dea9390914&AppID=10333&usr=xiaoyujie&pwd=356a192b7913b04c545";
            appcan.frame.open("content", url, 0, parseInt(titHeight) + parseInt(content));
            alert(2);
        });