xtype：在EXTJS的可视化组件部署中的一种机制，即通过指定xtype的值，来告诉容量如何初始化所包含的级件，如xtype:"textfiled",表示使用Ext.form.TextFile来进行初始化当前组件。
xtype Class ------------- ------------------ box Ext.BoxComponent button Ext.Button buttongroup Ext.ButtonGroup colorpalette Ext.ColorPalette component Ext.Component container Ext.Container cycle Ext.CycleButton dataview Ext.DataView datepicker Ext.DatePicker editor Ext.Editor editorgrid Ext.grid.EditorGridPanel flash Ext.FlashComponent grid Ext.grid.GridPanel listview Ext.ListView panel Ext.Panel progress Ext.ProgressBar propertygrid Ext.grid.PropertyGrid slider Ext.Slider spacer Ext.Spacer splitbutton Ext.SplitButton tabpanel Ext.TabPanel treepanel Ext.tree.TreePanel viewport Ext.ViewPort window Ext.Window Toolbar components --------------------------------------- paging Ext.PagingToolbar toolbar Ext.Toolbar tbbutton Ext.Toolbar.Button (deprecated; use button) tbfill Ext.Toolbar.Fill tbitem Ext.Toolbar.Item tbseparator Ext.Toolbar.Separator tbspacer Ext.Toolbar.Spacer tbsplit Ext.Toolbar.SplitButton (deprecated; use splitbutton) tbtext Ext.Toolbar.TextItem Menu components --------------------------------------- menu Ext.menu.Menu colormenu Ext.menu.ColorMenu datemenu Ext.menu.DateMenu menubaseitem Ext.menu.BaseItem menucheckitem Ext.menu.CheckItem menuitem Ext.menu.Item menuseparator Ext.menu.Separator menutextitem Ext.menu.TextItem Form components --------------------------------------- form Ext.FormPanel checkbox Ext.form.Checkbox checkboxgroup Ext.form.CheckboxGroup combo Ext.form.ComboBox datefield Ext.form.DateField displayfield Ext.form.DisplayField field Ext.form.Field fieldset Ext.form.FieldSet hidden Ext.form.Hidden htmleditor Ext.form.HtmlEditor label Ext.form.Label numberfield Ext.form.NumberField radio Ext.form.Radio radiogroup Ext.form.RadioGroup textarea Ext.form.TextArea textfield Ext.form.TextField timefield Ext.form.TimeField trigger Ext.form.TriggerField Chart components --------------------------------------- chart Ext.chart.Chart barchart Ext.chart.BarChart cartesianchart Ext.chart.CartesianChart columnchart Ext.chart.ColumnChart linechart Ext.chart.LineChart piechart Ext.chart.PieChart Store xtypes --------------------------------------- arraystore Ext.data.ArrayStore directstore Ext.data.DirectStore groupingstore Ext.data.GroupingStore jsonstore Ext.data.JsonStore simplestore Ext.data.SimpleStore (deprecated; use arraystore) store Ext.data.Store xmlstore Ext.data.XmlStore
defaults：xtypes的默认值，如：
defaults:{xtype:"textfield",width:180},
items:[{fieldLabel:"帐号"},{fieldLabel:"密码"}],