title: How to add clickhandler to the subrow of the celltablebuilder
body: <p>I am able to build custom rows with celltablebuilder. When clicking on a particular anchor cell, I am able to build additional subrows for that row. This subrow has buttons, when clicking on the button I have do some action. I am able to add buttons with clickhandler in the subrow, but when clicking on the button nothing is happening clickhandler is not firing. </p>
  
  <p>Can anybody please help.</p>
  
  <pre><code>protected void buildRowImpl(GridDTO rowValue, int absRowIndex ) {
    buildRows(rowValue, absRowIndex, true);
    if (showingFriends.contains(rowValue.getComponentId())) {
       buildAdditonalRows( absRowIndex, gridDTO);
    }
  
  }
  private void buildAdditonalRows(int index, GridDTO rowValue, ){ 
       TableRowBuilder row = startRow();
       td = row.startTD();
       if(rowValue.getXpath() != null){
      //td.text(rowValue.getXpath());
      renderCell(td, createContext(1), cellTable.getColumn(1), rowValue);
   }else{
      td.text("");
   }
       td.endTD();
       td = row.startTD();
       Button button = new Button ();
   button.setText("Save");
   button.addClickHandler(new ClickHandler() {
   @Override
   public void onClick(ClickEvent event) {
       Window.alert("ssss");
       }
   });
   DivBuilder div = td.startDiv();
   div.html(new afeHtmlBuilder().appendHtmlConstant(button.toString()).toSafeHtml());
   div.end();
       td.endTD();
       row.endTR();
  }
  </code></pre>