title: How to add click handler to Celltable ImageCell?
body: <p>How do I add a click handler to an <code>ImageCell</code>?
  This is what I have:</p>
  
  <pre><code>ImageCell btn= new ImageCell();
  Column&lt;Contact,String&gt; column = new Column&lt;Contact,String&gt;(btn) 
  {
      @Override
      public String getValue(Contact c) 
      {
          return c.imageLocation;
      }
  };
  column.setFieldUpdater(new FieldUpdater&lt;Contact,String&gt;()
  {
      public void update(int index, Contact c, String value) 
      {   
          Window.alert("clicked");
      }           
  });
  </code></pre>