I just started working with Sencha Touch and I'm absolutely loving it. I am working on a sample sign-in form. I would like to add exit button functionality to it but am stumped as to how to do it. Normal 'window.close()' is not working. So I'm hoping someone could point me to a solution that works.

var signInForm = new Ext.form.FormPanel({
            fullscreen: true,
            standardSubmit: true,
            scroll: 'vertical',
            items: [{
                    xtype: 'fieldset',
                    title: 'Sign in',
                    defaults: {
                        labelAlign: 'center'
                    items: [
                            xtype: 'textfield',
                            name : 'username',
                            label: 'User name:',
                            value: 'username',
                            autoCapitalize : false
                            xtype: 'passwordfield',
                            name : 'password',
                            value: 'password',
                            label: 'Password :'

            dockedItems: [
                    xtype: 'toolbar',
                    dock: 'top',
                    items: [ {
                            xtype: 'button',
                            text: 'Exit',
                            ui: 'forward',
                            handler: function(){
Thank you