button diabling

by Alexander Novikov

HTML

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8" />
<link href="http://cdn.sencha.com/ext/gpl/4.2.1/resources/css/ext-all.css" rel="stylesheet" />
<script src="http://cdn.sencha.com/ext/gpl/4.2.1/ext-all-debug.js"></script>
</head>
<body></body>
</html>

JavaScript

Ext.onReady(function() {
        
        Ext.widget('viewport', {
            renderTo: Ext.getBody(),
            layout: {
				type: 'vbox',
				align: 'stretch'
            },
            items: [
				{
					xtype: 'grid',
					itemId: 'my-letters',
					flex: 1,
					title: 'Буквы',
					selModel: {
						allowDeselect: true
					},
					columns: [
						{
							dataIndex: 'letter',
							text: 'letter'
						}
					],
					store: {
						fields: ['letter'],
						data: [{letter: 'a'}, {letter: 'b'}, {letter: 'c'}]
					},
					listeners: {
						selectionchange: function(selectionModel) {
							var addButton = Ext.ComponentQuery.query('[itemId="my-add-number-button"]')[0];
							addButton.setDisabled(!selectionModel.hasSelection());
						}
					}
				}, {
					xtype: 'grid',
					itemId: 'my-numbers',
					flex: 1,
					title: 'Цифры',
					columns: [
						{
							dataIndex: 'number',
							text: 'number'
						}
					],
					store: {
						fields: ['number'],
						data: [{number: 1}, {number: 2}, {number: 3}]
					},
					tbar: [
						{
                            xtype: 'button',
							itemId: 'my-add-number-button',
							text: 'Add Number',
							disabled: true
						}
					]
				}
            ]
        });
        
    });