Loading mask in sencha touch form submit
===

I have just started building app with sencha touch 2 i was trying to submit a from that i did now i want to display a loading mask at the time of submitting form. How can i dot that? I have tried serveral ways didnt get success. <br><br>
Please help me out

    Ext.define('AddressBook.view.Login', {
        extend: 'Ext.form.Panel',
        xtype: 'login',
        requires: ['Ext.form.*'],
        config: {
            xtype: 'formpanel',
            title: '<img src="resources/images/logo.png" width="180px"/>  ',
            iconCls: 'user',
            layout: 'vbox',
    		style: 'border:none;',
            items: [
    	{
                xtype: 'fieldset',
                title: 'Service Seeker Login',
                scrolable: true,
                items: [{
                    xtype: 'emailfield',
                    name: 'useremail',
                    placeHolder: 'Username or Email',
                    allowBlank: false
                }, {xtype:'spacer',  style: 'background-color: #EEE; height:20px; border:none;'}, {
                    xtype: 'passwordfield',
                    name: 'password',
    	placeHolder: 'Password',
                    allowBlank: false
                },{xtype:'spacer',  style: 'background-color: #EEE; height:20px; border:none;'},{
                xtype: 'checkboxfield',
                name : 'Remember',
               labelWidth: '80%' ,
                label: 'Remember me',
                value: 'remember'
            }, {
                    xtype: 'hiddenfield',
                    name: 'type',
                    value: 'user'
                }]
            }, {
                xtype: 'button',
                text: 'LOGIN',
    	    id: 'LoginButon',
                ui: 'confirm',
                width: '75px',
                handler: function () {
    	 //iniate loading screen for user
    	var myMask = new Ext.LoadMask(Ext.getBody(), {msg:"Please wait..."});
                    var form = this.up('formpanel');
                    var values = form.getValues();
                    if (values.useremail && values.password) {
                        form.submit({
                       url: 'http://mysite/mobilelogin',
                            method: 'POST',
                            success: function (form, result) {
                                if (result.go) {
    			myMask.show();
    			localStorage.setItem('userName',values.useremail);
                              		var indexPanel = Ext.create('AddressBook.view.Contacts');
    			Ext.Viewport.add(indexPanel);
    			Ext.Viewport.setActiveItem(indexPanel,{type: 'slide', direction: 'right'});
                                }
                            },
                            failure: function (form, result) {
                                Ext.Msg.alert('', result.message);
                            }
                        });
                    } else {
                        Ext.Msg.alert('Error', 'Both username and password are required.');
                    }
                }
            }
            }]
    });

I have posted this in sencha website also.
http://www.sencha.com/forum/showthread.php?190430-Simple-Form-example-with-Ajax-or-Connection-to-backend&p=851571#post851571
