extjs grid grouping 关闭和展开

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: '关闭所有',
                text: '关闭所有',
                enableToggle: true,
                pressed: true,
                handler: function(){
                    var me=this;
                    var view = me.up('grid');
                    console.log(view);
                    view.view.features[0].collapseAll();
                }
            }, {
                    tooltip: '展开所有',
                    text: '展开所有',
                    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);
            }
        },
         '100%',
        height: '100%',
        renderTo: Ext.getBody()
    });
});