why my initialize is no fire

I follow some sample code from google and wonder why initialize method is not fire(extjs 4.21). Can someone help?

below is my code:

Ext.define('Ext4Example.view.stock.StockPanel', { extend: 'Ext.form.Panel', alias: 'widget.stockpanel', config: { height: 455, id: 'FoodPanel', layout: { type: 'vbox' }, scrollable: 'vertical', items: [ { xtype: 'panel', height: 47, id: 'rowTitle', layout: { type: 'hbox' } } ] }, initialize: function () { console.log('gg'); }});