EXTJS4:如何改变grid某一个单元格的背景颜色

测试环境：ext-4.1.0-gpl

JS CODE:

Ext.onReady(function () {Ext.widget('grid', {title: 'Users',store: {fields: ['name', 'email', 'online'],data: [{ 'name': 'Lisa', "email": "lisa@", "online": true },{ 'name': 'Bart', "email": "bart@", "online": false },{ 'name': 'Homer', "email": "home@", "online": true },{ 'name': 'Marge', "email": "marge@", "online": true }]},columns: [{header: 'Name',dataIndex: 'name',renderer: function (value, meta, record) {meta.tdCls = record.get('online') ? 'user-online' : 'user-offline';return value;}},{ header: 'Email', dataIndex: 'email', flex: 1 },{ header: 'Online', dataIndex: 'online' }],width: 400,renderTo: 'output'});});

所用到的自定义CSS ：

.x-grid-cell.user-online{background-color: #9fc;}.x-grid-cell.user-offline{background-color: #ffc;}