title: ExtJS 4: Prevent changing tab using TabBar
body: <p>I don't use tab panel just tab bar, and have to prevent changing tab by some criteria.</p>
  
  <p>In ExtJS docs I found <code>change</code> event for <code>Ext.tab.Bar</code>, but it fires when tab is already changed. So <code>preventDefault()</code> and <code>return false</code> are not working in this case.</p>
  
  <p>Second I tried is set <code>Ext.tab.Tab.handler</code> property when tabs were initialized, but it fires when tab button is already clicked. So <code>preventDefault()</code> and <code>return false</code> don't work too.</p>
  
  <p>Can ony body help with this? How can I prevent changing tabs using only <code>Ext.tab.Tab</code> and <code>Ext.tab.Bar</code>?</p>
  
  <p>Thx.</p>