如何在Eclipse RCP插件的同一视图中删除当前显示的barchart（jfreechart）并显示新的barchart？

Question

I am creating barchart in a view of RCP plugin. The data to be displayed in the graph comes from the sqlite3 database file. The code I have written displays the barchart onto the view based on the date provided as input which we can select by using calender. sqlite3 connects to the database file and queries based on the date and gets the barchart data. Jfreechart is used to create the barchart and ChartComposite displays it onto the view.

The problem is when I select multiple dates one after another and ask to display, all the graphs are displayed on the same view, which i dont require. the output must be as follows, when i select the date for second time, the present graph must be deleted and new graph must be displayed. I tried to add dispose() in the code but its not working.

Following is my code for the same,

public class BarChartDisplay extends ViewPart {

Text searchfield = null;
String path = SelectDataBase.path;
public static int error=0;
public static int info=0;
public static int critical=0;
public static int warning=0;



public BarChartDisplay() {
    // TODO Auto-generated constructor stub
}

@Override
public void createPartControl(Composite parent) {
    // TODO Auto-generated method stub

    //Composite A:
    final Composite mainComposite = new Composite(parent, SWT.NONE);
    GridData mainLayoutData = new GridData(SWT.FILL, SWT.FILL, true, true);
    mainLayoutData.horizontalSpan = 1;
    mainComposite.setLayoutData(mainLayoutData);
    GridLayout outerLayout = new GridLayout();
    outerLayout.marginTop = 30;
    outerLayout.marginLeft = 20;
    outerLayout.marginRight = 20;
    mainComposite.setLayout(outerLayout);

    //Composite B:
    final Composite selectComposite = new Composite(mainComposite, SWT.NONE);
    GridData layoutData = new GridData(SWT.FILL, SWT.FILL, true, true);
    layoutData.horizontalSpan = 1;
    selectComposite.setLayoutData(layoutData);
    GridLayout layout = new GridLayout(4, false);
    selectComposite.setLayout(layout);

    //Composite C:
    final Composite barchartComposite = new Composite(mainComposite, SWT.NONE);
    GridData layoutData2 = new GridData(SWT.FILL, SWT.FILL, true, true);
    layoutData2.horizontalSpan = 1;
    barchartComposite.setLayoutData(layoutData2);
    GridLayout layout2 = new GridLayout(1, false);
    barchartComposite.setLayout(layout2); 


    final CalendarCombo ccombo = new CalendarCombo(selectComposite, SWT.READ_ONLY | SWT.FLAT);
    GridData layoutDataCal = new GridData(150, 40);

    ccombo.computeSize(SWT.DEFAULT, SWT.DEFAULT);
    ccombo.showCalendar();
    ccombo.setLayoutData(layoutDataCal);


    org.eclipse.swt.widgets.Button button = new org.eclipse.swt.widgets.Button(selectComposite, SWT.PUSH);
    button.setText("Go");



button.addListener(SWT.Selection, new Listener() {
    public void handleEvent(Event e) {
      switch (e.type) {
      case SWT.Selection:

        error = 0;
        info = 0;
        warning = 0;
        critical = 0;

        DB db = new DB();
        Connection conn = null;
        conn = db.ConnTable(path);
        Statement statement;
        try {
            statement = conn.createStatement();
            String query = null;
            String textfielddata = ccombo.getDateAsString();

            System.out.println(textfielddata);

            query = "select priority from log where creation_date = '"+ textfielddata +"'";


            System.out.println(query);
            ResultSet rs = statement.executeQuery(query);

            while (rs.next()) {

                int  prioritydata = rs.getInt("priority");

                if (prioritydata == 1)
                    error++;
                else if (prioritydata == 2)
                    info++;
                else if (prioritydata == 3)
                    warning++;
                else if (prioritydata == 4)
                    critical++;
            }


        } catch (SQLException er) {
            // TODO Auto-generated catch block
            er.printStackTrace();
        }

        System.out.println("after query");          


      final CategoryDataset dataset = createDataset();
      final JFreeChart chart = createChart(dataset);

      ChartComposite frame = new ChartComposite(barchartComposite,SWT.NONE,chart,true);       

      frame.setLayoutData(new GridData(GridData.FILL_BOTH));
      frame.pack();
      frame.setVisible(true);
      frame.setChart(chart);
      frame.forceRedraw();
      barchartComposite.getLayout();

      break;
      }
    }
  });


}

 /**
 * Returns a sample dataset.
 * 
 * @return The dataset.
 */
private CategoryDataset createDataset() {

    // row keys...
    final String series1 = "First";


    // column keys...
    final String category1 = "error";
    final String category2 = "info";
    final String category3 = "warning";
    final String category4 = "critical";


    // create the dataset...
    final DefaultCategoryDataset dataset = new DefaultCategoryDataset();

    dataset.addValue(10, series1, category1);
    dataset.addValue(5, series1, category2);
    dataset.addValue(6, series1, category3);
    dataset.addValue(9, series1, category4);


    return dataset;

}

/**
 * Creates a sample chart.
 * 
 * @param dataset  the dataset.
 * 
 * @return The chart.
 */
private JFreeChart createChart(final CategoryDataset dataset) {

    // create the chart...
    final JFreeChart chart = ChartFactory.createBarChart(
        "Priority BarChart",         // chart title
        "priority",               // domain axis label
        "Value",                  // range axis label
        dataset,                  // data
        PlotOrientation.VERTICAL, // orientation
        true,                     // include legend
        true,                     // tooltips?
        false                     // URLs?
    );

    // NOW DO SOME OPTIONAL CUSTOMISATION OF THE CHART...

    // set the background color for the chart...
    chart.setBackgroundPaint(Color.white);

    // get a reference to the plot for further customisation...
    final CategoryPlot plot = chart.getCategoryPlot();
    plot.setBackgroundPaint(Color.lightGray);
    plot.setDomainGridlinePaint(Color.white);
    plot.setRangeGridlinePaint(Color.white);

    // set the range axis to display integers only...
    final NumberAxis rangeAxis = (NumberAxis) plot.getRangeAxis();
    rangeAxis.setStandardTickUnits(NumberAxis.createIntegerTickUnits());

    // disable bar outlines...
    final BarRenderer renderer = (BarRenderer) plot.getRenderer();
    renderer.setDrawBarOutline(false);

    // set up gradient paints for series...
    final GradientPaint gp0 = new GradientPaint(
        0.0f, 0.0f, Color.blue, 
        0.0f, 0.0f, Color.lightGray
    );

    renderer.setSeriesPaint(0, gp0);


    final CategoryAxis domainAxis = plot.getDomainAxis();
    domainAxis.setCategoryLabelPositions(
        CategoryLabelPositions.createUpRotationLabelPositions(Math.PI / 6.0)
    );
    // OPTIONAL CUSTOMISATION COMPLETED.

    return chart;

}   

@Override
public void setFocus() {
    // TODO Auto-generated method stub

}

}

Answer 1

您不需要处理图表，只需使用新选择的日期重新创建数据集，然后使用chart.getPlot().setDataset(new_dataset)刷新具有新数据的图表。