title: GWT ValueChangeHandler and getting before value
body: <p>I want to get values of my textBox before change its value and after changed its value.</p>
  
  <pre><code>String beforeValue = "";
  TextBox textBox = new TextBox();
      textBox.addFocusHandler(new FocusHandler() {
  
          public void onFocus(final FocusEvent event) {
              beforeValue = textBox.getText();
  
          }
      });
      textBox.addValueChangeHandler(new ValueChangeHandler&lt;String&gt;() {
  
          public void onValueChange(final ValueChangeEvent&lt;String&gt; event) {
              System.out.println("Before value is " + beforeValue);
              System.out.println("After value is " + textBox.getText());
          }
      });
  </code></pre>
  
  <p>As above codes , I need two handlers (<strong>FocusHandler and ValueChangeHadler</strong>)  to get before value and after value . My question is how can I get it by one Handler or another simple and easy way ? I don't want to use two handlers to get it. Any suggestions would be appreciated. <strong><em>Thanks in advance !</em></strong></p>