java - 防止 Java 框架的多个实例

Question

我正在开发的应用程序涉及根据用户选择从 JPanel 创建的框架。我试图阻止用户在选择同一项目两次时启动同一帧的多个实例。这是我为此目的编写的条件。

主类:

public void showPieGraphFrame()
{
    final PieGraph gPieGraph = new PieGraph("Traffic Type Distribution", counterOne, counterTwo);
    gPieGraph.pack();
    RefineryUtilities.positionFrameOnScreen(gPieGraph, 0.35, 0.03);

    if(!gPieGraph.isVisible())  
    {
    gPieGraph.setVisible(true);
    }
}

我想要防止多个实例的 PieGraph 类:

public class PieGraph extends ApplicationFrame implements ActionListener {

    public PieGraph(final String title) {
        super(title);

        // create a menubar
        setJMenuBar(createMenuBar());

        // create a dataset...
        final PieDataset dataset = trafficTypeDataset();

        // create the chart...
        final JFreeChart chart = createChart(dataset);

        // add the chart to a panel...
        final ChartPanel chartPanel = new ChartPanel(chart);
        chartPanel.setPreferredSize(new java.awt.Dimension(width, height));
        setContentPane(chartPanel);
    }

    private JFreeChart createChart(final PieDataset dataset) {

        final JFreeChart chart = ChartFactory.createPieChart("Test Chart", dataset, false, false, false);

        final PiePlot plot = (PiePlot) chart.getPlot();

        return chart;
    }

但是，它不起作用，您仍然可以多次启动同一框架。我怎样才能防止这种情况发生？

Answer 1

How can I prevent this?

将框架交换为模态 JDialog 或 JOptionPane。