Datagrid 显示数据是最新的，但$('#datagrid').datagrid('getSelections')取得的选中数据不是最新的

项目中使用了easyui的datagrid和dialog,dialog中包括了一个datagrid.

<div id="dlg-role-edit" href="" class="easyui-dialog" modal="true" 
        style="width:500px;height:300px;padding:15px 10px" closed="true" 
       buttons="#dlg-buttons-user_roles">
	<input type="hidden" id="currentSelectUserId" name="currentSelectUserId" />
         
        <table id="dg-user-roles"></table>
</div>
<div id="dlg-buttons-user_roles">
	<a href="#" class="easyui-linkbutton" iconCls="icon-ok" onclick="saveUserRoles()">Save</a>
	<a href="#" class="easyui-linkbutton" iconCls="icon-cancel" onclick="javascript:$('#dlg-role-edit').dialog('close')">Cancel</a>
</div>

 页面点击编辑按钮时，弹出这个dialog,并刷新datagrid "dg-user-roles'中的数据，点击dialog的save按钮时，保存数据。javascript 代码如下：

          function editRole() {
	    	var row = $('#dg').datagrid('getSelected');
			if (row){
				document.getElementById("currentSelectUserId").value= row.userId;
				//alert(document.getElementById("currentSelectUserId").value);
				
				$('#dlg-role-edit').dialog('open')
				$('#dlg-role-edit').dialog('setTitle','Edit user\'s roles');
				
				$('#dg-user-roles').datagrid({
		    		title:'Current user:' +row.userName,
				    iconCls:'',
				    url:'${ctx}/accountmanagement/user/listUserRoles.html?userId='+row.userId,
				    idField:'roleId',
				    height:200,
				    pagination:false,
				    fitColumns:true,
				    columns:[[
				        {field:'checked',checkbox:true},
				        {field:'roleName',title:'Role Name',width:200},
				        {field:'roleDesc',title:'Role Description',width:200}
				    ]], 
				    onLoadSuccess:function() {
				    	var rows = $('#dg-user-roles').datagrid('getRows')
						var rowcount = rows.length;
						for(var i=0; i<rowcount; i++){
							alert(rows[i].roleId);
							if(rows[i].checked) {
								$('#dg-user-roles').datagrid('selectRow',i);	
							} else {
								$('#dg-user-roles').datagrid('unselectRow',i);	
							}
						}
				    }
		    	});
			} else {
				$.messager.alert('',"Please select one user to edit roles.");
			}
	    }
	    
	    function saveUserRoles() {
	    	var currentSelectUserId = document.getElementById("currentSelectUserId").value;
	    	var selectedRows = $('#dg-user-roles').datagrid('getSelections');
	    	alert(currentSelectUserId);
	    	alert(selectedRows);
	    	alert(selectedRows.length);
	    	var rowcount = selectedRows.length;
	    	var var_roleIds = "";
	    	if(rowcount == 0) {
	    		$.messager.alert('',"Please at least select a role for user.");
	    	} else {
	    		for(var i=0; i<rowcount; i++){
	    			var_roleIds +=","+selectedRows[i].roleId;
	    		}
	    		if(var_roleIds != "" && var_roleIds.length != 0) {
	    			var_roleIds = var_roleIds.substr(1);
	    		}
	    		alert("var_roleIds: " + var_roleIds);
	    		$.post('${ctx}/accountmanagement/user/userEditRoles.html',{userId:currentSelectUserId,roleIds:var_roleIds},function(result){
					if (result.success){
						$.messager.alert('',result.msg);
						$('#dlg-role-edit').dialog('close', 'forceClose');
					} else {
						$.messager.alert('',result.msg);
					}
				},'json');
	    	}
	    }

 使用上面的代码在再次打开dialog时显示的是新数据，但是通过$('#dg-user-roles').datagrid('getSelections')得到的却是上次点开时选中的的旧数据。为解决这个问题，将上面的js代码改为下面，重点是先取消所有选中，然后重新加载

var is_dg_user_roles_init = false;
	    function editRole() {
	    	var row = $('#dg').datagrid('getSelected');
			if (row){
				document.getElementById("currentSelectUserId").value= row.userId;
				//alert(document.getElementById("currentSelectUserId").value);
				
				
				$('#dlg-role-edit').dialog('open')
				$('#dlg-role-edit').dialog('setTitle','Edit user\'s roles');
				
				
				if(!is_dg_user_roles_init) {
					alert("firsttime");
					$('#dg-user-roles').datagrid({
			    		title:'Current user:' +row.userName,
					    iconCls:'',
					    url:'${ctx}/accountmanagement/user/listUserRoles.html?userId='+row.userId,
					    idField:'roleId',
					    height:200,
					    pagination:false,
					    fitColumns:true,
					    columns:[[
					        {field:'checked',checkbox:true},
					        {field:'roleName',title:'Role Name',width:200},
					        {field:'roleDesc',title:'Role Description',width:200}
					    ]], 
					    onLoadSuccess:function() {
					    	var rows = $('#dg-user-roles').datagrid('getRows')
							var rowcount = rows.length;
							for(var i=0; i<rowcount; i++){
								alert(rows[i].roleId);
								if(rows[i].checked) {
									$('#dg-user-roles').datagrid('selectRow',i);	
								} else {
									$('#dg-user-roles').datagrid('unselectRow',i);	
								}
							}
					    }
			    	});
			    	is_dg_user_roles_init = true;
				} else {
					alert("not firsttime");
                                        $('#dg-user-roles').datagrid('clearSelections');
                                        $('#dg-user-roles').datagrid('options').url = '${ctx}/accountmanagement/user/listUserRoles.html?userId='+row.userId;
					$('#dg-user-roles').datagrid('reload');
				}
				
			} else {
				$.messager.alert('',"Please select one user to edit roles.");
			}
	    }
	    
	    function saveUserRoles() {
	    	var currentSelectUserId = document.getElementById("currentSelectUserId").value;
	    	var selectedRows = $('#dg-user-roles').datagrid('getSelections');
	    	alert(currentSelectUserId);
	    	alert(selectedRows);
	    	alert(selectedRows.length);
	    	var rowcount = selectedRows.length;
	    	var var_roleIds = "";
	    	if(rowcount == 0) {
	    		$.messager.alert('',"Please at least select a role for user.");
	    	} else {
	    		for(var i=0; i<rowcount; i++){
	    			var_roleIds +=","+selectedRows[i].roleId;
	    		}
	    		if(var_roleIds != "" && var_roleIds.length != 0) {
	    			var_roleIds = var_roleIds.substr(1);
	    		}
	    		alert("var_roleIds: " + var_roleIds);
	    		$.post('${ctx}/accountmanagement/user/userEditRoles.html',{userId:currentSelectUserId,roleIds:var_roleIds},function(result){
					if (result.success){
						$.messager.alert('',result.msg);
						$('#dlg-role-edit').dialog('close', 'forceClose');
					} else {
						$.messager.alert('',result.msg);
					}
				},'json');
	    	}
	    }