Grid header join,

Vaadin 6 / 7 / 8 Framework UI
1

I want to add additional header row by joining two column,

Following code is not working for me, no error but no results,

Column<RoutingPointData, String> c1= addColumn(person → “Move”,
new ButtonRenderer(clickEvent → {this.setDetailsVisible((RoutingPointData) clickEvent.getItem(), !this.isDetailsVisible((RoutingPointData) clickEvent.getItem()));}));

HeaderRow groupingHeader = prependHeaderRow();

groupingHeader.join(
groupingHeader.getCell(c1),
groupingHeader.getCell(c2),
groupingHeader.getCell(c3)).setText(“testing1”);;

      groupingHeader.join(
     groupingHeader.getCell(c4),
     groupingHeader.getCell(c5)).setText("testing2");;;
2

Can you show the entire code? for example a Github link?