如何使Timer类在Java中每10秒加载一个jfreechart?

时间:2015-11-09 17:24:23

标签: java swing timer jframe jfreechart

我有一个使用jfreechart API显示网站登录的JFrame。它是一个条形图,数据集来自SQL数据库。

java项目加载图表,图表显示当前的网站登录。由于数据集每秒都在变化,因此条形图应该是动态的。我使用Timer类来做到这一点。它每10秒运行一次loadLogonChart()。到目前为止,我没有遇到任何问题。但问题是它确实在10秒内更新了图表。但是,在20秒后,它会在我首先运行表单时将值加载回来。然后这个过程一遍又一遍地重复。我使用的代码如下。我无法弄清楚它有什么问题。

public final class MainForm extends javax.swing.JFrame implements ActionListener{


private static int AUTO_UPDATE_CHARTS = 10000;


public MainForm() throws SQLException {
    //Timer for the barchart    
    Timer timerChart = new Timer(AUTO_UPDATE_CHARTS, new AbstractAction() {

        @Override
        public void actionPerformed(ActionEvent e) {
            try {
                loadLogonChart();
            } catch (SQLException ex) {
                Logger.getLogger(MainForm.class.getName()).log(Level.SEVERE, null, ex);
            }
        }
    }); 
    timerChart.start();


    //LOAD THE FORM
    loadForm();

}



public void loadForm() throws SQLException{
    initComponents();
    loadLogonChart();

}

public void loadLogonChart() throws SQLException{
     //database class that I need for the barchart datasets
    Database db = new Database();

    DefaultCategoryDataset dataset = new DefaultCategoryDataset();
    JFreeChart chart = ChartFactory.createBarChart("Web Site Activity Chart", "Days", "# of visits", dataset, PlotOrientation.VERTICAL, false, true, false);
    CategoryPlot catPlot = chart.getCategoryPlot();

    try {
        dataset.setValue(db.showMonday(), "logon", "Monday");
        dataset.setValue(db.showTuesday(), "logon", "Tuesday");
        dataset.setValue(db.showWednesday(), "logon", "Wednesday");
        dataset.setValue(db.showThursday(), "logon", "Thursday");
        dataset.setValue(db.showFriday(), "logon", "Friday");
        dataset.setValue(db.showSaturday(), "logon", "Saturday");
        dataset.setValue(db.showSunday(), "logon", "Sunday");

        chart = ChartFactory.createBarChart("Web Site Activity Chart", "Days", "# of visits", dataset, PlotOrientation.VERTICAL, false, true, false);
        ChartPanel myChart = new ChartPanel(chart);
        myChart.setMouseWheelEnabled(true);


        BarRenderer renderer = (BarRenderer) catPlot.getRenderer();
        DecimalFormat decimalFormat = new DecimalFormat("##.##");
        renderer.setBaseItemLabelGenerator(new StandardCategoryItemLabelGenerator("{2}",decimalFormat));
        catPlot.setRenderer(renderer);
        renderer.setBasePositiveItemLabelPosition(new ItemLabelPosition(ItemLabelAnchor.CENTER, TextAnchor.TOP_LEFT));
        renderer.setItemLabelsVisible(true);
        chart.getCategoryPlot().setRenderer(renderer);

        //renderer.setBaseItemLabelGenerator(CategoryItemLabelGenerator generator)

        chartPanel.setLayout(new java.awt.BorderLayout());
        chartPanel.add(myChart,BorderLayout.CENTER);
        chartPanel.revalidate();
        chartPanel.validate();

    } catch (SQLException ex) {
        Logger.getLogger(MainForm.class.getName()).log(Level.SEVERE, null, ex);
    }

}

1 个答案:

答案 0 :(得分:1)

    chartPanel.add(myChart,BorderLayout.CENTER);
    chartPanel.revalidate();
    chartPanel.validate();

在我看来,您试图继续向chartPanel添加不同的组件。添加组件不会删除以前的组件。

Swing绘制最后添加的组件,以便旧面板显示在新面板的顶部。尝试:

    chartPanel.removeAll();
    chartPanel.add(myChart,BorderLayout.CENTER);
    chartPanel.revalidate();
    chartPanel.validate(); // not needed since you do revalidate
    chartPanel.repaint();