GridPanel只好显示一行数据

GridPanel只能显示一行数据
入门级的例子，只是就显示一行，大家帮忙看下。

Ext.BLANK_IMAGE_URL="../../ext/resources/images/default/s.gif";

Ext.onReady(function(){

	var cm = new Ext.grid.ColumnModel([

	{header:"id",dataIndex:"id"},

	{header:"姓名",dataIndex:"name"},

	{header:"email",dataIndex:"email"},

	{header:"性别",dataIndex:"sex"},

	{header:"年龄",dataIndex:"age"}

	]);

	var fields = ["id","name","email","sex","age"];

	var data = [["1","JIm","cc@msn.com","0","22"],["2","Naha","blue@msn.com","1","23"]];

	var store = new Ext.data.SimpleStore({

			fields:fields,

			data:data

	});

	var grid = new Ext.grid.GridPanel({

		cm:cm,

		store:store

	});

	grid.render(Ext.getBody());

});

------解决方案--------------------
加个高度就好了
var grid = new Ext.grid.GridPanel({
        cm:cm,
        height:300,
        store:store
    });