xtype可作为Ext控件的简写，都会对应一个Ext控件。当然这里你也可以自定义这个xtype，通过自定义的Ext控件来绑定，
主要由Ext.reg方法去注册xtype。Ext.all.js里面包含的xtype包含：

xtype            Class
-------------    ------------------
box              {@link Ext.BoxComponent}
button           {@link Ext.Button}
buttongroup      {@link Ext.ButtonGroup}
colorpalette     {@link Ext.ColorPalette}
component        {@link Ext.Component}
container        {@link Ext.Container}
cycle            {@link Ext.CycleButton}
dataview         {@link Ext.DataView}
datepicker       {@link Ext.DatePicker}
editor           {@link Ext.Editor}
editorgrid       {@link Ext.grid.EditorGridPanel}
flash            {@link Ext.FlashComponent}
grid             {@link Ext.grid.GridPanel}
listview         {@link Ext.ListView}
multislider      {@link Ext.slider.MultiSlider}
panel            {@link Ext.Panel}
progress         {@link Ext.ProgressBar}
propertygrid     {@link Ext.grid.PropertyGrid}
slider           {@link Ext.slider.SingleSlider}
spacer           {@link Ext.Spacer}
splitbutton      {@link Ext.SplitButton}
tabpanel         {@link Ext.TabPanel}
treepanel        {@link Ext.tree.TreePanel}
viewport         {@link Ext.ViewPort}
window           {@link Ext.Window}

Toolbar components
---------------------------------------
paging           {@link Ext.PagingToolbar}
toolbar          {@link Ext.Toolbar}
tbbutton         {@link Ext.Toolbar.Button}        (deprecated; use button)
tbfill           {@link Ext.Toolbar.Fill}
tbitem           {@link Ext.Toolbar.Item}
tbseparator      {@link Ext.Toolbar.Separator}
tbspacer         {@link Ext.Toolbar.Spacer}
tbsplit          {@link Ext.Toolbar.SplitButton}   (deprecated; use splitbutton)
tbtext           {@link Ext.Toolbar.TextItem}

Menu components
---------------------------------------
menu             {@link Ext.menu.Menu}
colormenu        {@link Ext.menu.ColorMenu}
datemenu         {@link Ext.menu.DateMenu}
menubaseitem     {@link Ext.menu.BaseItem}
menucheckitem    {@link Ext.menu.CheckItem}
menuitem         {@link Ext.menu.Item}
menuseparator    {@link Ext.menu.Separator}
menutextitem     {@link Ext.menu.TextItem}

Form components
---------------------------------------
form             {@link Ext.form.FormPanel}
checkbox         {@link Ext.form.Checkbox}
checkboxgroup    {@link Ext.form.CheckboxGroup}
combo            {@link Ext.form.ComboBox}
compositefield   {@link Ext.form.CompositeField}
datefield        {@link Ext.form.DateField}
displayfield     {@link Ext.form.DisplayField}
field            {@link Ext.form.Field}
fieldset         {@link Ext.form.FieldSet}
hidden           {@link Ext.form.Hidden}
htmleditor       {@link Ext.form.HtmlEditor}
label            {@link Ext.form.Label}
numberfield      {@link Ext.form.NumberField}
radio            {@link Ext.form.Radio}
radiogroup       {@link Ext.form.RadioGroup}
textarea         {@link Ext.form.TextArea}
textfield        {@link Ext.form.TextField}
timefield        {@link Ext.form.TimeField}
trigger          {@link Ext.form.TriggerField}

Chart components
---------------------------------------
chart            {@link Ext.chart.Chart}
barchart         {@link Ext.chart.BarChart}
cartesianchart   {@link Ext.chart.CartesianChart}
columnchart      {@link Ext.chart.ColumnChart}
linechart        {@link Ext.chart.LineChart}
piechart         {@link Ext.chart.PieChart}

Store xtypes
---------------------------------------
arraystore       {@link Ext.data.ArrayStore}
directstore      {@link Ext.data.DirectStore}
groupingstore    {@link Ext.data.GroupingStore}
jsonstore        {@link Ext.data.JsonStore}
simplestore      {@link Ext.data.SimpleStore}      (deprecated; use arraystore)
store            {@link Ext.data.Store}
xmlstore         {@link Ext.data.XmlStore}