java - JPanel添加但不显示 "in time"

Question

我有一个 JFrame，它根据您单击的 MenuItem 显示 JPanel。它有效，但现在我需要在将 JPanel 添加到框架并显示它后调用一个方法(因为我在该面板内使用 JFreeChart，我必须调用 chartPanel.repaint() 当 JPanel 可见时):

this.getContentPane().add( myjpanel, BorderLayout.CENTER ); //this = JFrame
this.validate();
myjpanel.methodCalledOnceDisplayed();

看起来还好吗？ myjpanel 真的被显示了吗？好像不是:

public void methodCalledOnceDisplayed() {
    chartPanel.repaint()
}

这不起作用(chartPanel.getChartRenderingInfo().getPlotInfo().getSubplotInfo(0) 抛出 IndexOutOfBoundsException)。这意味着调用重绘时 JPanel 不可见，我测试了以下内容:

public void methodCalledOnceDisplayed() {
    JOptionPane.showMessageDialog(null,"You should see myjpanel now");
    chartPanel.repaint()
}

现在它工作了，我在警报后面看到 myjpanel，正如预期的那样，重新绘制了 chartPanel 并且没有发生异常。

编辑:SSCCE(需要 jfreechart 和 jcommon:http://www.jfree.org/jfreechart/download.html)

import java.awt.BorderLayout;import java.awt.EventQueue;import java.awt.Font;import javax.swing.JButton;import javax.swing.JFrame;import javax.swing.JLabel;import javax.swing.JOptionPane;import javax.swing.JPanel;import javax.swing.border.EmptyBorder;import org.jfree.chart.ChartMouseEvent;import org.jfree.chart.ChartMouseListener;import org.jfree.chart.JFreeChart;import org.jfree.chart.plot.CombinedDomainXYPlot;import org.jfree.chart.plot.PlotOrientation;import org.jfree.chart.plot.XYPlot;import org.jfree.chart.ChartPanel;import org.jfree.data.time.TimeSeries;import org.jfree.data.time.TimeSeriesCollection;import org.jfree.data.xy.XYDataset;import java.awt.event.ActionListener;import java.awt.event.ActionEvent;public class Window extends JFrame {    private JPanel contentPane;    public static void main(String[] args) {        EventQueue.invokeLater(new Runnable() {            public void run() {                try {                    Window frame = new Window();                    frame.setVisible(true);                } catch (Exception e) {                    e.printStackTrace();                }            }        });    }    public Window() {        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);        setBounds(100, 100, 700, 500);        contentPane = new JPanel();        contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));        contentPane.setLayout(new BorderLayout(0, 0));        setContentPane(contentPane);        JButton clickme = new JButton("Click me");        clickme.addActionListener(new ActionListener() {            public void actionPerformed(ActionEvent arg0) {                contentPane.removeAll();                MyJPanel mypanel = new MyJPanel();                contentPane.add( mypanel, BorderLayout.CENTER );                validate();                mypanel.methodCalledOnceDisplayed();            }        });        contentPane.add( clickme, BorderLayout.NORTH );        JPanel example = new JPanel();        example.add( new JLabel("Example JPanel") );        contentPane.add( example, BorderLayout.CENTER );    }}class MyJPanel extends JPanel implements ChartMouseListener {    private ChartPanel chartPanel;    private JFreeChart chart;    private XYPlot subplotTop;    private XYPlot subplotBottom;    private CombinedDomainXYPlot plot;    public MyJPanel() {        this.add( new JLabel("This JPanel contains the chart") );        createCombinedChart();        chartPanel = new ChartPanel(chart);        chartPanel.addChartMouseListener(this);        this.add( chartPanel );    }    private void createCombinedChart() {            plot = new CombinedDomainXYPlot();        plot.setGap(30);        createSubplots();        plot.add(subplotTop, 4);        plot.add(subplotBottom, 1);        plot.setOrientation(PlotOrientation.VERTICAL);        chart = new JFreeChart("Title", new Font("Arial", Font.BOLD,20), plot, true);    }    private void createSubplots() {        subplotTop = new XYPlot();        subplotBottom = new XYPlot();        subplotTop.setDataset(emptyDataset("Empty 1"));        subplotBottom.setDataset(emptyDataset("Empty 2"));    }    private XYDataset emptyDataset( String title ) {        TimeSeries ts = new TimeSeries(title);        TimeSeriesCollection tsc = new TimeSeriesCollection();        tsc.addSeries(ts);        return tsc;    }    @Override    public void chartMouseMoved(ChartMouseEvent e) {        System.out.println("Mouse moved!");    }    @Override    public void chartMouseClicked(ChartMouseEvent arg0) {}    public void methodCalledOnceDisplayed() {        JOptionPane.showMessageDialog(null,"Magic!"); //try to comment this line and see the console        chartPanel.repaint();        //now we can get chart areas        this.chartPanel.getChartRenderingInfo().getPlotInfo().getSubplotInfo(0).getDataArea();        this.chartPanel.getChartRenderingInfo().getPlotInfo().getSubplotInfo(1).getDataArea();    }}

看看使用和不使用 JOptionPane 会发生什么。

Answer 1

An explanation of why is this happening would be great.

您可能会从下面的变体中获得一些见解。注意

• Swing GUI 对象应该仅在 event dispatch thread 上构造和操作(EDT) 原因建议here .

• EDT 继续处理事件，如示例所示，即使用户交互仅限于模式对话框也是如此。

• 调用 repaint()使用 ChartPanel 时不需要 .

• 首选 CardLayout 或 JTabbedPane 优于手动容器操作。

• 而不是调用 setPreferredSize() , 覆盖 getPreferredSize() ，正如所讨论的here .

附录:您删除了显示问题的两行......

ChartRenderingInfo是在图表呈现之前不存在的动态数据。当图表在后台更新时，模态对话框处理事件；没有它，您可以通过将其包装在 Runnable 中来安排您的方法适用于invokeLater() :

EventQueue.invokeLater(new Runnable() {

    @Override
    public void run() {
        myPanel.methodCalledOnceDisplayed();
    }
});

更好的方案是访问 ChartRenderingInfo在您知道数据有效的监听器中，即由 ChartPanel 实现的监听器.

import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.Date;
import java.util.Random;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.Timer;
import javax.swing.border.EmptyBorder;
import org.jfree.chart.ChartPanel;
import org.jfree.chart.JFreeChart;
import org.jfree.chart.axis.DateAxis;
import org.jfree.chart.axis.NumberAxis;
import org.jfree.chart.plot.CombinedDomainXYPlot;
import org.jfree.chart.plot.PlotOrientation;
import org.jfree.chart.plot.PlotRenderingInfo;
import org.jfree.chart.plot.XYPlot;
import org.jfree.chart.renderer.xy.XYLineAndShapeRenderer;
import org.jfree.data.time.Day;
import org.jfree.data.time.TimeSeries;
import org.jfree.data.time.TimeSeriesCollection;
import org.jfree.data.xy.XYDataset;

/**
* @see https://stackoverflow.com/a/14894894/230513
*/
public class Test extends JFrame {

    private JPanel panel;

    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {

            @Override
            public void run() {
                Test frame = new Test();
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public Test() {
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        final MyJPanel myPanel = new MyJPanel();
        panel = new JPanel() {

            @Override
            public Dimension getPreferredSize() {
                return myPanel.getPreferredSize();
            }
        };
        panel.setBorder(new EmptyBorder(5, 5, 5, 5));
        panel.setLayout(new BorderLayout());
        add(panel);

        myPanel.start();
        JButton clickme = new JButton("Click me");
        clickme.addActionListener(new ActionListener() {

            @Override
            public void actionPerformed(ActionEvent arg0) {
                panel.removeAll();
                panel.add(myPanel, BorderLayout.CENTER);
                validate();
                EventQueue.invokeLater(new Runnable() {

                    @Override
                    public void run() {
                        myPanel.methodCalledOnceDisplayed();
                    }
                });
            }
        });
        panel.add(clickme, BorderLayout.NORTH);
        JPanel example = new JPanel();
        example.add(new JLabel("Example JPanel"));
        panel.add(example, BorderLayout.CENTER);
    }

    private static class MyJPanel extends JPanel {

        private static final Random r = new Random();
        private ChartPanel chartPanel;
        private JFreeChart chart;
        private XYPlot subplotTop;
        private XYPlot subplotBottom;
        private CombinedDomainXYPlot plot;
        private Timer timer;
        private Day now = new Day(new Date());

        public MyJPanel() {
            this.add(new JLabel("Chart panel"));
            createCombinedChart();
            chartPanel = new ChartPanel(chart);
            this.add(chartPanel);
            timer = new Timer(1000, new ActionListener() {

                @Override
                public void actionPerformed(ActionEvent e) {
                    update(subplotTop);
                    update(subplotBottom);
                }
            });
            timer.start();
        }

        public void start() {
            timer.start();
        }

        private void update(XYPlot plot) {
            TimeSeriesCollection t = (TimeSeriesCollection) plot.getDataset();
            for (int i = 0; i < t.getSeriesCount(); i++) {
                TimeSeries s = t.getSeries(i);
                s.add(now, Math.abs(r.nextGaussian()));
                now = (Day) now.next();
            }
        }

        private void createCombinedChart() {
            plot = new CombinedDomainXYPlot();
            plot.setGap(30);
            createSubplots();
            plot.add(subplotTop, 4);
            plot.add(subplotBottom, 1);
            plot.setOrientation(PlotOrientation.VERTICAL);
            chart = new JFreeChart("Title",
                JFreeChart.DEFAULT_TITLE_FONT, plot, true);
            plot.setDomainAxis(new DateAxis("Domain"));
        }

        private void createSubplots() {
            subplotTop = new XYPlot();
            subplotBottom = new XYPlot();
            subplotTop.setDataset(emptyDataset("Set 1"));
            subplotTop.setRenderer(new XYLineAndShapeRenderer());
            subplotTop.setRangeAxis(new NumberAxis("Range"));
            subplotBottom.setDataset(emptyDataset("Set 2"));
            subplotBottom.setRenderer(new XYLineAndShapeRenderer());
            subplotBottom.setRangeAxis(new NumberAxis("Range"));
        }

        private XYDataset emptyDataset(String title) {
            TimeSeriesCollection tsc = new TimeSeriesCollection();
            TimeSeries ts = new TimeSeries(title);
            tsc.addSeries(ts);
            return tsc;
        }

        public void methodCalledOnceDisplayed() {
            PlotRenderingInfo plotInfo =
                this.chartPanel.getChartRenderingInfo().getPlotInfo();
            for (int i = 0; i < plotInfo.getSubplotCount(); i++) {
                System.out.println(plotInfo.getSubplotInfo(i).getDataArea());
            }
            JOptionPane.showMessageDialog(null, "Magic!");
        }
    }
}

附录:一个额外的迭代来说明 ChartMouseListener并清理一些 Unresolved 问题。

import java.awt.BorderLayout;
import java.awt.EventQueue;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.Date;
import java.util.Random;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.Timer;
import org.jfree.chart.ChartMouseEvent;
import org.jfree.chart.ChartMouseListener;
import org.jfree.chart.ChartPanel;
import org.jfree.chart.JFreeChart;
import org.jfree.chart.axis.DateAxis;
import org.jfree.chart.axis.NumberAxis;
import org.jfree.chart.entity.ChartEntity;
import org.jfree.chart.plot.CombinedDomainXYPlot;
import org.jfree.chart.plot.PlotOrientation;
import org.jfree.chart.plot.XYPlot;
import org.jfree.chart.renderer.xy.XYLineAndShapeRenderer;
import org.jfree.data.time.Day;
import org.jfree.data.time.TimeSeries;
import org.jfree.data.time.TimeSeriesCollection;
import org.jfree.data.xy.XYDataset;

/**
 * @see https://stackoverflow.com/a/14894894/230513
 */
public class Test {

    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {

            @Override
            public void run() {
                Test t = new Test();
            }
        });
    }

    public Test() {
        JFrame f = new JFrame();
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        final MyJPanel myPanel = new MyJPanel();
        f.add(myPanel, BorderLayout.CENTER);
        f.pack();
        f.setLocationRelativeTo(null);
        f.setVisible(true);
        myPanel.start();
    }

    private static class MyJPanel extends JPanel {

        private static final Random r = new Random();
        private ChartPanel chartPanel;
        private JFreeChart chart;
        private XYPlot subplotTop;
        private XYPlot subplotBottom;
        private CombinedDomainXYPlot plot;
        private Timer timer;
        private Day now = new Day(new Date());

        public MyJPanel() {
            createCombinedChart();
            chartPanel = new ChartPanel(chart);
            this.add(chartPanel);
            timer = new Timer(1000, new ActionListener() {

                @Override
                public void actionPerformed(ActionEvent e) {
                    update(subplotTop);
                    update(subplotBottom);
                    now = (Day) now.next();
                }
            });
            chartPanel.addChartMouseListener(new ChartMouseListener() {

                @Override
                public void chartMouseClicked(ChartMouseEvent e) {
                    final ChartEntity entity = e.getEntity();
                    System.out.println(entity + " " + entity.getArea());
                }

                @Override
                public void chartMouseMoved(ChartMouseEvent e) {
                }
            });
        }

        public void start() {
            timer.start();
        }

        private void update(XYPlot plot) {
            TimeSeriesCollection t = (TimeSeriesCollection) plot.getDataset();
            for (int i = 0; i < t.getSeriesCount(); i++) {
                TimeSeries s = t.getSeries(i);
                s.add(now, Math.abs(r.nextGaussian()));
            }
        }

        private void createCombinedChart() {
            plot = new CombinedDomainXYPlot();
            createSubplots();
            plot.add(subplotTop, 4);
            plot.add(subplotBottom, 1);
            plot.setOrientation(PlotOrientation.VERTICAL);
            chart = new JFreeChart("Title",
                JFreeChart.DEFAULT_TITLE_FONT, plot, true);
            plot.setDomainAxis(new DateAxis("Domain"));
        }

        private void createSubplots() {
            subplotTop = new XYPlot();
            subplotBottom = new XYPlot();
            subplotTop.setDataset(emptyDataset("Set 1"));
            subplotTop.setRenderer(new XYLineAndShapeRenderer());
            subplotTop.setRangeAxis(new NumberAxis("Range"));
            subplotBottom.setDataset(emptyDataset("Set 2"));
            subplotBottom.setRenderer(new XYLineAndShapeRenderer());
            subplotBottom.setRangeAxis(new NumberAxis("Range"));
        }

        private XYDataset emptyDataset(String title) {
            TimeSeriesCollection tsc = new TimeSeriesCollection();
            TimeSeries ts = new TimeSeries(title);
            tsc.addSeries(ts);
            return tsc;
        }
    }
}