Vaadin Charts and drilldown

Hi all!
I have a project where the data in the main chart is represented as a bar chart and the data in a drilldown should be line/area/column chart.

Is this possible?

I've found a way to solve my problem, but my solution is incomplete.

I override the drillup listener:

@Override
    public void onDrillup(ChartDrillupEvent event) {
        Chart ch = (Chart) event.getComponent();
        ch.getConfiguration().getChart().setType(ChartType.AREA);
        ch.getConfiguration().getxAxis().setType(AxisType.DATETIME);
        ch.drawChart();
    }

Invoking in on the chart the method addChartDrillupListener().
In this way when the drillup event is fired I can change my chart configuration. This works fine.

Now I want to do the same thing with the drilldown event but I can't figure the way to do that!
Can someone help me?