ExtJS Grid使用SimpleStore、多选框的方法

///<reference path="./vswd-ext_2.0.2.js" />
Ext.onReady(function(){
var data = [
[1,"wilson.fu",10],
[2,"wilson.fu2",20],
[3,"wilson.fu3",30]
];

var sqldata = new Array() ;
for(var i=0;i<10;i++)
{
sqldata.push([i.toString(),"wilson.fu" + i.toString(),10*i]);
}

var sm = new Ext.grid.CheckboxSelectionModel({handleMouseDown:Ext.emptyFn});
var cm = new Ext.grid.ColumnModel([
sm,
{header:"编号",dataIndex:"id",sortable:true},
{header:"姓名",dataIndex:"name"},
{header:"排序值",dataIndex:"ordernum",sortable:true}
]);

var store = new Ext.data.SimpleStore({
fields:[
{name:"id"},
{name:"name"},
{name:"ordernum"}
]
});

store.loadData(sqldata);

var gd = new Ext.grid.GridPanel({
renderTo:"grid",
cm:cm,
sm:sm,
store:store,
loadMask:true
});

Ext.get("btn").on("click",function(){
var selections = gd.getSelectionModel().getSelections();
debugger
//得到选择的行的值
});

});