title: How to get the value of checkbox
body: <p>How to get the value of a check box?</p>
  
  <pre><code>var tb = new Ext.Toolbar();
  
  tb.add({
                  xtype: 'checkbox',
                  boxLabel: 'Expand Groups by Default',
                  id: 'GetChkBoxValue',
                  checked: true,
                  handler: function() {
                      alert(this.getValue())
                  }
         });
  </code></pre>
  
  <p>Is it possible to get the value of the checkbox outside tb.I have done something like this but it is not firing</p>
  
  <pre><code>Ext.getCmp('GetChkBoxValue').getValue(); 
  </code></pre>