Use Ext.data.JsonP for cross-domain

Ext.data.JsonP.request({
url: 'http://www.example.com/api/example',
params: {
apiKey: '1234'
},
callbackKey: 'myCallbackFn',
success: function(){
//task on successful request
},
failure: function(){
//task on failed request
},
scope: this
});