extjs grid grouping 關閉和展開

Ext.onReady(function() {    var store = Ext.create('Ext.data.Store', {        storeId: 'employeeStore',        fields: ['name', 'seniority', 'department'],        groupField: 'department',        data: {            'employees': [                {"name": "Michael Scott", "seniority": 7, "department": "Management"},                {"name": "Dwight Schrute", "seniority": 2, "department": "Sales"},                {"name": "Jim Halpert", "seniority": 3, "department": "Sales"},                {"name": "Kevin Malone", "seniority": 4, "department": "Accounting"},                {"name": "Angela Martin", "seniority": 5, "department": "Accounting"}            ]        },        proxy: {            type: 'memory',            reader: {                type: 'json',                root: 'employees'            }        }    });   var grid = Ext.create('Ext.grid.Panel', {        title: 'Employees',       name:'mygrid',        store: Ext.data.StoreManager.lookup('employeeStore'),        dockedItems: [{            dock: 'top',            xtype: 'toolbar',            items: [{                tooltip: '關閉全部',                text: '關閉全部',                enableToggle: true,                pressed: true,                handler: function(){                    var me=this;                    var view = me.up('grid');                    console.log(view);                    view.view.features[0].collapseAll();                }            }, {                    tooltip: '展開全部',                    text: '展開全部',                    enableToggle: true,                    pressed: true,                    handler: function(){                        var me=this;                        var view = me.up('grid');                        console.log(view);                        view.view.features[0].expandAll();                    }                }]        }],        columns: [            {text: 'Name', dataIndex: 'name'},            {text: 'Seniority', dataIndex: 'seniority'}        ],        features: [            {                ftype: 'grouping'            }        ],        listeners: {            groupclick: function (view, node, group, e, eOpts) {               view.features[0].collapseAll();               view.features[0].expand(group);            }        },        width: '100%',        height: '100%',        renderTo: Ext.getBody()    });});