如何在组件绘制时创建“请稍候”Swing 对话框

对于 Swing 来说仍然相对较新，但经过几个小时的搜索，我无法在网上找到答案，因此写了这篇文章（抱歉，如果已经回答但我忽略了它）。

我在 Swing 应用程序中使用 JFreeChart。有些图表相对较重（180k 数据点），并且 JFreeChart 的 ChartPanel 需要大约 6 秒来执行其第一个 PaintComponent()。

因此，我想在组件绘制时在对话框中显示“请稍候”消息（无需使用 SwingWorker 显示进度）。我尝试重写 PaintComponent 方法，但不幸的是该消息从未出现在屏幕上（我猜线程直接进入绘制图表，而不花时间绘制对话框）。

我的代码如下所示：

public class CustomizedChartPanel extends ChartPanel{

private static final long serialVersionUID = 1L;
private JDialog dialog = null;
boolean isPainted = false;

public CustomizedChartPanel(JFreeChart chart) { super(chart); }

@Override
public void paintComponent(Graphics g) {
    //At first paint (which can be lengthy for large charts), show "please wait" message
    if (! isPainted){
        dialog = new JDialog();
        dialog.setUndecorated(true);
        JPanel panel = new JPanel();
        panel.add(new JLabel("Please wait"));
        dialog.add(panel);
        dialog.pack();
        GuiHelper.centerDialog(dialog); //Custom code to center the dialog on the screen
        dialog.setVisible(true);
        dialog.repaint();
    }

    super.paintComponent(g);

    if (! isPainted){
        isPainted = true;
        dialog.dispose();
            super.repaint();
        }
}
}

任何有关如何解决此问题/最佳实践的指示将不胜感激！

谢谢， 托马斯

UPDATE:

感谢您的提示和辩论：非常有帮助。

我开始使用 invokeLater() 实现建议的解决方案，因为我担心 JLayer 解决方案无法工作，因为它也在 EDT 上运行。

不幸的是，当invokeLater()调用paintComponent()时，我遇到了空指针异常。

我的代码如下所示：

    @Override
public void paintComponent(Graphics graph) {
    //At first paint (which can be lengthy for large charts), show "please wait" message
    if (! isPainted){
        isPainted = true;
        dialog = new JDialog();
        dialog.setUndecorated(true);
        JPanel panel = new JPanel();
        panel.add(new JLabel("Please wait"));
        panel.add(new JLabel("Please wait !!!!!!!!!!!!!!!!!!!!!!!!!!!!!"));
        dialog.add(panel);
        dialog.pack();
        GuiHelper.centerDialog(dialog); //Custom code to center the dialog on the screen
        dialog.setVisible(true);
        dialog.repaint();
        RunnableRepaintCaller r = new RunnableRepaintCaller(this, graph, dialog);
        SwingUtilities.invokeLater(r);
    }
    else super.paintComponent(graph); //NULL POINTER EXCEPTION HERE (invoked by runnable class)
}

可运行的类是：

public class RunnableRepaintCaller implements Runnable{
private ChartPanel target;
private Graphics g;
private JDialog dialog;

public RunnableRepaintCaller(ChartPanel target, Graphics g, JDialog dialog){
    this.target = target;
    this.g = g;
    this.dialog = dialog;
}

@Override
public void run() {
    System.out.println(g);
    target.paintComponent(g);
    dialog.dispose();
}
}

再次强调，任何指针将不胜感激！

Thomas

这是一个示例和/但它使用 SwingWorker。您应该认真考虑使用它，因为如果操作系统以某种方式使您的框架无效并且 JFreeChart 的加载是在 EDT（事件调度线程）上完成的，那么您的 GUI 将看起来冻结。

它还允许您在处理数据时提供更好的用户反馈。 （抱歉，代码有点长，但大多数有趣的代码都在 initUI 和 SwingWorker 中）。

注意：您可以使用 JLayer（如果您使用 Java 7）代替对话框，但这在我的示例中是不必要的。

该代码的灵感很大来自http://www.vogella.com/articles/JFreeChart/article.html http://www.vogella.com/articles/JFreeChart/article.html

/**
 * This code was directly taken from: http://www.vogella.com/articles/JFreeChart/article.html
 * All credits goes to him for this code.
 * 
 * Thanks to him.
 */

import java.util.List;

import javax.swing.JDialog;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
import javax.swing.SwingWorker;

import org.jfree.chart.ChartFactory;
import org.jfree.chart.ChartPanel;
import org.jfree.chart.JFreeChart;
import org.jfree.chart.plot.PiePlot3D;
import org.jfree.data.general.DefaultPieDataset;
import org.jfree.data.general.PieDataset;
import org.jfree.util.Rotation;

public class PieChart extends JFrame {

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                initUI();
            }
        });
    }

    protected static void initUI() {
        // First we create the frame and make it visible
        final PieChart demo = new PieChart("Comparison");
        demo.setSize(500, 270);
        demo.setVisible(true);
        // Then we display the dialog on that frame
        final JDialog dialog = new JDialog(demo);
        dialog.setUndecorated(true);
        JPanel panel = new JPanel();
        final JLabel label = new JLabel("Please wait...");
        panel.add(label);
        dialog.add(panel);
        dialog.pack();
        // Public method to center the dialog after calling pack()
        dialog.setLocationRelativeTo(demo);

        // allowing the frame and the dialog to be displayed and, later, refreshed
        SwingWorker<JFreeChart, String> worker = new SwingWorker<JFreeChart, String>() {

            @Override
            protected JFreeChart doInBackground() throws Exception {
                publish("Loading dataset");
                // simulating the loading of the Dataset
                try {
                    System.out.println("Loading dataset");
                    Thread.sleep(2000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                // This will create the dataset 
                PieDataset dataset = demo.createDataset();
                publish("Loading JFreeChart");
                // simulating the loading of the JFreeChart
                try {
                    System.out.println("Loading JFreeChart");
                    Thread.sleep(2000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                // based on the dataset we create the chart
                JFreeChart chart = demo.createChart(dataset, "Which operating system are you using?");
                // we put the chart into a panel
                return chart;
            }

            @Override
            protected void process(List<String> chunks) {
                label.setText(chunks.get(0));
                dialog.pack();
                dialog.setLocationRelativeTo(demo);
                dialog.repaint();
            }

            @Override
            protected void done() {
                try {
                    // Retrieve the created chart and put it in a ChartPanel
                    ChartPanel chartPanel = new ChartPanel(this.get());
                    // add it to our frame
                    demo.setContentPane(chartPanel);
                    // Dispose the dialog.
                    dialog.dispose();
                    // We revalidate to trigger the layout
                    demo.revalidate();
                    // Repaint, just to be sure
                    demo.repaint();
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }

        };
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                     worker.execute();
            }
        });
        dialog.setVisible(true);
    }

    public PieChart(String applicationTitle) {
        super(applicationTitle);
    }

    /** * Creates a sample dataset */

    private PieDataset createDataset() {
        DefaultPieDataset result = new DefaultPieDataset();
        result.setValue("Linux", 29);
        result.setValue("Mac", 20);
        result.setValue("Windows", 51);
        return result;

    }

    /** * Creates a chart */

    private JFreeChart createChart(PieDataset dataset, String title) {

        JFreeChart chart = ChartFactory.createPieChart3D(title, // chart title
                dataset, // data
                true, // include legend
                true, false);
        PiePlot3D plot = (PiePlot3D) chart.getPlot();
        plot.setStartAngle(290);
        plot.setDirection(Rotation.CLOCKWISE);
        plot.setForegroundAlpha(0.5f);
        return chart;

    }

}