public void refresh(Map<String, List<String[]>> viewData) {
this.prviewData = viewData;
initChartData(viewData);
jfreeChartComp.setChart(computeChart());
jfreeChartComp.forceRedraw();
}
/** create a chart with empty dataset,so as to clear the blocking key chart. */
public void clearChart() {
JFreeChart jfreechart =
createBarChart("Number of rows", new HistogramDataset(), false); // $NON-NLS-1$
jfreeChartComp.setChart(jfreechart);
jfreeChartComp.forceRedraw();
}