title: Exts4 MVC, How to grep textfield in controller
body: <p>In view,</p>
  
  <pre><code>{
     xtype: 'textfield',
     fieldLabel: 'Test Field',
     name: 'testField'
  }
  </code></pre>
  
  <p>I want to grep that textfield in controller to hook Keyup event.</p>
  
  <p>I tried,</p>
  
  <pre><code>this.control({
    'input[name='testfield']' : {
       afterrender : function(c){
          console.log(c); // nothing happened.
          c.getEl().on('keyup', function (evt, el) {
                  console.log(evt.getKey());
          });
       }
    }
  });
  </code></pre>
  
  <p>but it does not work,</p>
  
  <p>How can I grep that textbox in controller and hook keyup event?</p>
  
  <p>Anybody know, please advise me.</p>
  
  <p>Thanks</p>