Sencha Touch2.3.1 large FIle Upload to server

Hi ,

I am building an app using Sencha Touch 2.3.1 for uploading an large file to a webserver. In first phase, I have to accept file from user and save it locally on device. Then there is a Sync button which user has to tap for uploading all images to webserver. Trying to use Ext.Ajax but it's not working for me. I am unable to send file from local storage area.

Ext.Ajax.request({

url: <Server URL>,

headers: {

'X-Charset': document.characterSet,

'Content-Type': 'multipart/form-data'

},

params: {

'reply[text]': 'this is a dummy text',

'reply[attachment]': <location of file on local device>

},

callback: function(options, success, response) {

// callback logic

},

scope: this

});

Please suggest something.