title: How to reveal a presenterwidget/presenter in it's parent only on some event in gwt platform?
body: <p>I'm doing an application in GWT-Platform. I've layouted my main page using dock layout. In the west part of the dock layout I'll be having some links (<code>Anchor</code>). Based on what I'm clicking I have to display a <code>PresenterWidget</code>/ <code>presenter</code>  in the center.</p>
  
  <p>How can I achieve this? i've tried like this with presenter</p>
  
  <pre><code>@UiHandler("myAnchor")
  public void onClicked(ClickEvent event) {
      mainContent.clear();
      mainContent.add(newPageinCenter);
  }
  </code></pre>
  
  <p>in the Parent presenter view i have used <code>SimpleLayoutPanel</code> for center of dock</p>
  
  <pre><code>&lt;g:center&gt;
  &lt;g:SimpleLayoutPanel ui:field="mainContent"&gt;        
  &lt;/g:SimpleLayoutPanel&gt;
  &lt;/g:center&gt;
  </code></pre>
  
  <p>and in the child again i'm using a docklayout panel to add some more custom widgets to it's 
  sides like </p>
  
  <pre><code>&lt;g:DockLayoutPanel&gt;
      &lt;g:north size='60' unit='EM'&gt;
          &lt;g:SimpleLayoutPanel&gt;
              &lt;widgets:CustWid1 ui:field="policySelPane" /&gt;
          &lt;/g:SimpleLayoutPanel&gt;
      &lt;/g:north&gt;
      &lt;g:center&gt;
          &lt;g:VerticalSplitPanel&gt;
              &lt;widgets:CustWid2 ui:field="createPolicyPane" /&gt;
              &lt;widgets:CustWid3 ui:field="stackPane" /&gt;
          &lt;/g:VerticalSplitPanel&gt;
      &lt;/g:center&gt;
      &lt;g:south size='60'&gt;
          &lt;g:FlowPanel&gt;
              &lt;g:Button ui:field="computePremium"&gt;Compute Premium&lt;/g:Button&gt;
          &lt;/g:FlowPanel&gt;
      &lt;/g:south&gt;
  &lt;/g:DockLayoutPanel&gt;
  </code></pre>
  
  <p>but i'm able to seen only north and i'm using <code>RevealRootLayoutContentEvent</code> in my child <code>Presenter</code> also what is my mistake    </p>