extjs4 打开pdf文件

buttons: [{
    text :'OPEN DOCUMENT',
    formBind : true,
    handler:function() {
        new Ext.window.Window({
            title: 'Document',
            height: 800,
            width: 800,
            layout: 'fit',
            items: [{
                html: '<iframe src="..."></iframe>'
            }]
        });
    }
}]

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网上找的一段代码，如果是动态的话，应该要获取到item下的html的值，然后赋值

var mConfig = {        mediaType   :'PDFFRAME',   //this is the most reliable cross-browser        url         : 'servlet/PdfServlet?invoice=2319283',       unsupportedText : 'Acrobat Viewer is not Installed',   resizable   : true