title: ExtJS 4 RadioGroup Change Event Fires Twice
body: <p>I'm using ExtJS 4.0.7, am new to Ext, and am using the new MVC architecture. I have a RadioGroup that, upon change, I want to use to reveal more UI elements. The problem is, that the change event fires twice for the RadioGroup. I'm assuming this is because both Radios fire an event for having their values change. </p>
  
  <p>Is there a way to listen for a change to either the RadioGroup or Radios with the same name that will fire only once? In my experience with jQuery and Flex, I would expect a RadioGroup to only fire once.</p>
  
  <p>Here's the RadioGroup code in my view:</p>
  
  <pre><code>items: [{
      xtype: 'radiogroup',
      id: 'WheatChoice',
      padding: '',
      layout: {
          padding: '-3 0 4 0',
          type: 'hbox'
      },
      fieldLabel: 'Choose Model',
      labelPad: 5,
      labelWidth: 80,
      allowBlank: false,
      columns: 1,
      flex: 1,
      anchor: '60%',
      items: [
          { xtype: 'radiofield', id: 'SpringWheat', padding: '2 10 0 0', fieldLabel: '', 
            boxLabel: 'Spring', name: 'wheat-selection', inputValue: '0', flex: 1 },
          { xtype: 'radiofield', id: 'WinterWheat', padding: '2 0 0 0', fieldLabel: '',
            boxLabel: 'Winter', name: 'wheat-selection', inputValue: '1', checked: true, flex: 1 }
       ]
  }]
  </code></pre>
  
  <p>Here's the relevant code in my Controller:</p>
  
  <pre><code>init: function() {
       this.control({
           '#WheatChoice': {
              change: this.onWheatChange
           }
       });
  },
  
  onWheatChange: function(field, newVal, oldVal) {
      //this fires twice
      console.log('wheat change');
  }
  </code></pre>