Sencha Touch TabBar添加按钮左侧的按钮

var tabBar = Ext.create('Ext.TabBar', {
    docked: 'bottom',
    items: [
        {
            title: 'Home',
            iconCls: 'home'
        },
        {
            title: 'Contact',
            iconCls: 'user'
        }
    ]
});

tabBar.add({
    title: 'Settings',
    iconCls: 'settings',
    handler: function() {
        console.log('Settings button clicked');
    }
});

var tabBar = Ext.create('Ext.TabBar', {
    docked: 'bottom',
    items: [
        {
            title: 'Home',
            iconCls: 'home'
        },
        {
            title: 'Contact',
            iconCls: 'user'
        }
    ]
});

tabBar.insert(0, {
    title: 'Settings',
    iconCls: 'settings',
    handler: function() {
        console.log('Settings button clicked');
    }
});