各位extjs达人,小弟初学,问个GridPanel滚动条的问题


var tset=null;
Ext.onReady(function(){Ext.QuickTips.init();
    
    var xg = Ext.grid;    // shared reader
    var reader = new Ext.data.ArrayReader({}, [
       {name: 'company'},
       {name: 'price', type: 'float'},
       {name: 'change', type: 'float'},
       {name: 'pctChange', type: 'float'},
       {name: 'lastChange', type: 'date', dateFormat: 'n/j h:ia'},
       {name: 'desc'}
    ]);var store=new Ext.data.Store({
proxy: new Ext.data.MemoryProxy(xg.dummyData),
        reader: reader
        //data: mydata
    });
    //store.load();
    //mydata=xg.dummyData;
    store.load();
var grid = new Ext.grid.GridPanel({
    store: store,
    columns: [
        {id:'company', header: "Company", width: 200, sortable: true, dataIndex: 'company'},
        {header: "Price", width: 120, sortable: true, renderer: Ext.util.Format.usMoney, dataIndex: 'price'},
        {header: "Change", width: 120, sortable: true, dataIndex: 'change'},
        {header: "% Change", width: 120, sortable: true, dataIndex: 'pctChange'},
        {header: "Last Updated", width: 135, sortable: true, renderer: Ext.util.Format.dateRenderer('m/d/Y'), dataIndex: 'lastChange'}
    ],
    viewConfig: {
        forceFit: true
    },
    //sm: new Ext.grid.RowSelectionModel({singleSelect:false}),
    width:600,
    height:300,
    frame:false,
    collapsible: true,
    animCollapse: false,
    title:'Framed with Checkbox Selection and Horizontal Scrolling',
    iconCls:'icon-grid',
    //autoHeight:true,
    autoScroll : true,
    renderTo: document.body
});
test=function(arraydata){
//改变数据源
grid.store.loadData(arraydata,false);};
});
var mydata2=[];
var mydata = [
    ['3m Co',71.72,0.02,0.03,'9/1 12:00am'],
    ['Alcoa Inc',29.01,0.42,1.47,'9/1 12:00am'],
    ['Altria Group Inc',83.81,0.28,0.34,'9/1 12:00am'],
    ['American Express Company',52.55,0.01,0.02,'9/1 12:00am'],
    ['American International Group, Inc.',64.13,0.31,0.49,'9/1 12:00am'],
    ['AT&T Inc.',31.61,-0.48,-1.54,'9/1 12:00am'],
    ['Boeing Co.',75.43,0.53,0.71,'9/1 12:00am'],
    ['Caterpillar Inc.',67.27,0.92,1.39,'9/1 12:00am']
    ];
Ext.grid.dummyData = [
    ['3m Co',71.72,0.02,0.03,'9/1 12:00am'],
    ['Alcoa Inc',29.01,0.42,1.47,'9/1 12:00am'],
    ['Altria Group Inc',83.81,0.28,0.34,'9/1 12:00am'],
    ['American Express Company',52.55,0.01,0.02,'9/1 12:00am'],
    ['American International Group, Inc.',64.13,0.31,0.49,'9/1 12:00am'],
    ['AT&T Inc.',31.61,-0.48,-1.54,'9/1 12:00am'],
    ['Boeing Co.',75.43,0.53,0.71,'9/1 12:00am'],
    ['Caterpillar Inc.',67.27,0.92,1.39,'9/1 12:00am'],
    ['Citigroup, Inc.',49.37,0.02,0.04,'9/1 12:00am'],
    ['E.I. du Pont de Nemours and Company',40.48,0.51,1.28,'9/1 12:00am'],
    ['Exxon Mobil Corp',68.1,-0.43,-0.64,'9/1 12:00am'],
    ['General Electric Company',34.14,-0.08,-0.23,'9/1 12:00am'],
    ['General Motors Corporation',30.27,1.09,3.74,'9/1 12:00am'],
    ['Hewlett-Packard Co.',36.53,-0.03,-0.08,'9/1 12:00am'],
    ['Honeywell Intl Inc',38.77,0.05,0.13,'9/1 12:00am'],
    ['Intel Corporation',19.88,0.31,1.58,'9/1 12:00am'],
    ['International Business Machines',81.41,0.44,0.54,'9/1 12:00am'],
    ['Johnson & Johnson',64.72,0.06,0.09,'9/1 12:00am'],
    ['JP Morgan & Chase & Co',45.73,0.07,0.15,'9/1 12:00am'],
    ['McDonald\'s Corporation',36.76,0.86,2.40,'9/1 12:00am'],
    ['Merck & Co., Inc.',40.96,0.41,1.01,'9/1 12:00am'],
    ['Microsoft Corporation',25.84,0.14,0.54,'9/1 12:00am'],
    ['Pfizer Inc',27.96,0.4,1.45,'9/1 12:00am'],
    ['The Coca-Cola Company',45.07,0.26,0.58,'9/1 12:00am'],
    ['The Home Depot, Inc.',34.64,0.35,1.02,'9/1 12:00am'],
    ['The Procter & Gamble Company',61.91,0.01,0.02,'9/1 12:00am'],
    ['United Technologies Corporation',63.26,0.55,0.88,'9/1 12:00am'],
    ['Verizon Communications',35.57,0.39,1.11,'9/1 12:00am'],
    ['Wal-Mart Stores, Inc.',45.45,0.73,1.63,'9/1 12:00am'],
    ['Walt Disney Company (The) (Holding Company)',29.89,0.24,0.81,'9/1 12:00am']
];这个是源码.extjs版本是2.2.1 ,上面我明明已经设置了 height和width 的固定值,autoScroll : true也设置了,但是为啥就是不出现滚动条呢??哪位好心人帮小弟看看...