datagrid 选中某行，翻页再翻回来，发现选中的行没有选中

 1     $(function(){
 2          $(‘#dg‘).datagrid({
 3              url:‘ContactServlet‘,
 4              toolbar:‘#tb‘,
 5              fit:true,
 6              fitColumns:true,
 7              rownumbers:true,
 8              pagination:true,
 9              idField : ‘id‘,//没有设置，就会出现翻页不选中
10              columns:[[    
11                        {field:‘id‘,title:‘id‘,checkbox:true},
12                        {field:‘lxr_xm‘,title:‘姓名‘,width:220,align:‘center‘},    
13                        {field:‘lxr_tel‘,title:‘电话‘,width:220,align:‘center‘},    
14                        {field:‘lxr_email‘,title:‘Email‘,width:220,align:‘center‘},     
15                        {field:‘lxr_qq‘,title:‘QQ‘,width:220,align:‘center‘},
16                        {field:‘lxr_lx‘,title:‘联系‘,width:220,align:‘center‘}  
17                    ]] 
18          });
19 
20     });