解决Extjs上传图片无法预览的解决方法

{
width: 450,
fileUpload: true,
fieldLabel: '选择图片',
items: [{
xtype: 'textfield',
id: 'up_forth',
name: 'up_forth',
inputType: 'file',
width: 300
}]
}

{
columnWidth: .18,
bodyStyle: ' margin:4px 10px 10px 5px',
layout: 'form',
items: [{
xtype: 'box',
autoEl: {
width: 150, height: 150,
tag: 'div',
id: 'browser_up_forth'
}
}]
}

var preview = function (myform, control_id) {
var img_reg = /\.([jJ][pP][gG]){1}$|\.([jJ][pP][eE][gG]){1}$|\.([gG][iI][fF]){1}$|\.([pP][nN][gG]){1}$|\.([bB][mM][pP]){1}$/
myform.on('render', function (f) {
myform.form.findField(control_id).on('render', function () {
Ext.get(control_id).on('change', function (field, newValue, oldValue) {
var obj = Ext.get(control_id).dom;
var url = getFullPath(obj);
if (img_reg.test(url)) {
var newPreview = Ext.get('browser_' + control_id).dom;
var showPic = Ext.get("showPic_" + control_id);
if (showPic != null) {
showPic.remove();//删除原来的图片
}
var imgDiv = document.createElement("div");
imgDiv.id = "showPic_" + control_id;
document.body.appendChild(imgDiv);
imgDiv.style.width = "150px";
imgDiv.style.height = "150px";
imgDiv.style.filter = "progid:DXImageTransform.Microsoft.AlphaImageLoader(sizingMethod = scale)";
imgDiv.filters.item("DXImageTransform.Microsoft.AlphaImageLoader").src = url;
newPreview.appendChild(imgDiv);
}
}, this);
}, this);
}, this);
}

//得到图片地址
function getFullPath(obj) {
if (obj) {
// ie
if (window.navigator.userAgent.indexOf("MSIE") >= 1) {
obj.select();
return document.selection.createRange().text;
}
// firefox
else if (window.navigator.userAgent.indexOf("Firefox") >= 1) {
if (obj.files) {
return obj.files.item(0).getAsDataURL();
}
return obj.value;
}
return obj.value;
}
}