在 ListCellRenderer 中呈现 JList 内容时出现 OutOfMemoryError

Question

我试图在 JList 的图表中表示一些数据。在我创建 ChartPanels here 的 JList 之前。现在我正在尝试XYSeriesCollection 的JList，然后在自定义ListCellRenderer 中呈现其内容。

但我在尝试通过拖动光标滚动 JScrollpane 时遇到了OutOfMemoryError。

Java 虚拟机选项：-d64 -Xmx400m

为什么会这样？我应该在渲染中更改什么？

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Component;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.util.Random;

import javax.swing.DefaultListModel;
import javax.swing.JFrame;
import javax.swing.JList;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.ListCellRenderer;
import javax.swing.ListSelectionModel;

import org.jfree.chart.ChartFactory;
import org.jfree.chart.ChartPanel;
import org.jfree.chart.JFreeChart;
import org.jfree.data.xy.XYSeries;
import org.jfree.data.xy.XYSeriesCollection;

/**
 * @see https://stackoverflow.com/a/40445144/230513
 */

public class ThumbnailChartsJList{

public static JScrollPane scrollPane;
public static JList<XYSeriesCollection> chartList;

public static void main(final String[] args) {

    EventQueue.invokeLater(new Runnable() {

        @Override
        public void run() {
            JFrame f = new JFrame("Test");
            JPanel panel = new JPanel(new BorderLayout());

            chartList = new ChartList();

            scrollPane = new JScrollPane(chartList,
                    JScrollPane.VERTICAL_SCROLLBAR_ALWAYS,
                    JScrollPane.HORIZONTAL_SCROLLBAR_NEVER);


            panel.add(scrollPane, BorderLayout.CENTER);
            f.setPreferredSize(new Dimension(1000,700));
            f.setContentPane(panel);
            f.pack();
            f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
            f.setVisible(true);
        }
    });

}

}

class ChartList extends JList<XYSeriesCollection>{

    private static final Random random = new Random();
    private static final int NumberCharts = 50;
    private static final int Samples = 200;

    private static final int W = 300;
    private static final int H = W;

    ChartList(){
        DefaultListModel<XYSeriesCollection> listModel = new DefaultListModel<XYSeriesCollection>();


        for (int i=0; i<NumberCharts; i++){
            XYSeriesCollection serie = createRandomSerie();
            listModel.addElement(serie);
        }
        this.setModel(listModel);
        this.setSelectionMode(ListSelectionModel.MULTIPLE_INTERVAL_SELECTION);
        this.setCellRenderer(new ChartListRenderer());
        this.setVisibleRowCount(0); //0 - dynamic rows
        this.setLayoutOrientation(JList.HORIZONTAL_WRAP);
        this.setSelectionForeground(Color.RED);
    }

    private static XYSeriesCollection createRandomSerie() {

        final XYSeries series = new XYSeries("Data");
        for (int i = 0; i < random.nextInt(Samples) + Samples; i++) {
            series.add(i, random.nextGaussian());
        }
        XYSeriesCollection dataset = new XYSeriesCollection(series);
        return dataset;    
    }

    static class ChartListRenderer implements ListCellRenderer<XYSeriesCollection> {

        @Override
        public Component getListCellRendererComponent(JList<? extends XYSeriesCollection> chartList, XYSeriesCollection serie, int index,
            boolean isSelected, boolean cellHasFocus) {

            JFreeChart chart = ChartFactory.createXYLineChart("Random", "counts", "samples", serie);

            ChartPanel chartPanel = new ChartPanel(chart, true, true, true, false, true){
                @Override
                public Dimension getPreferredSize() {
                return new Dimension(W, H);}
            };
            return chartPanel;
        }

    }
}

Answer 1

正如@PaL 建议的here，您的ListCellRenderer 可以创建JFreeChart 及其封闭ChartPanel 的单个 实例。当调用渲染器的getListCellRendererComponent() 实现时，它可以简单地更新图表绘图使用的数据集。结果很容易在所示的小堆中运行。

@Override
public Component getListCellRendererComponent(
    JList modelList, XYSeriesCollection series,
        int index, boolean isSelected, boolean hasFocus) {
    XYPlot plot = chart.getXYPlot();
    plot.setDataset(series);
    return chartPanel;
}

经测试：$ java -d64 -Xmx64m -cp .:$JFREE_LIB/* ModelListTest

import java.awt.Color;
import java.awt.Component;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.util.Random;

import javax.swing.DefaultListModel;
import javax.swing.JFrame;
import javax.swing.JList;
import javax.swing.JScrollPane;
import javax.swing.ListCellRenderer;
import javax.swing.ListSelectionModel;

import org.jfree.chart.ChartFactory;
import org.jfree.chart.ChartPanel;
import org.jfree.chart.JFreeChart;
import org.jfree.chart.plot.XYPlot;
import org.jfree.data.xy.XYSeries;
import org.jfree.data.xy.XYSeriesCollection;

/**
 * @see https://stackoverflow.com/q/46527131/230513
 * @see https://stackoverflow.com/a/40445144/230513
 */
public class ModelListTest {

    public static void main(final String[] args) {

        EventQueue.invokeLater(new Runnable() {

            @Override
            public void run() {
                JFrame f = new JFrame("Test");
                f.add(new JScrollPane(new ModelList()));
                f.pack();
                f.setSize(640, 480);
                f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                f.setVisible(true);
            }
        });
    }

    private static class ModelList extends JList<XYSeriesCollection> {

        private static final Random random = new Random();
        private static final int charts = 50;
        private static final int samples = 200;
        private static final int W = 300;
        private static final int H = W;

        ModelList() {
            DefaultListModel<XYSeriesCollection> listModel = new DefaultListModel<>();
            for (int i = 0; i < charts; i++) {
                listModel.addElement(createRandomSeries());
            }
            this.setModel(listModel);
            this.setSelectionMode(ListSelectionModel.MULTIPLE_INTERVAL_SELECTION);
            this.setCellRenderer(new ModelListRenderer());
            this.setVisibleRowCount(0);
            this.setLayoutOrientation(JList.HORIZONTAL_WRAP);
            this.setSelectionForeground(Color.RED);
        }

        private static XYSeriesCollection createRandomSeries() {
            final XYSeries series = new XYSeries("Data");
            for (int i = 0; i < random.nextInt(samples) + samples; i++) {
                series.add(i, random.nextGaussian());
            }
            XYSeriesCollection dataset = new XYSeriesCollection(series);
            return dataset;
        }

        private static class ModelListRenderer implements ListCellRenderer<XYSeriesCollection> {

            private JFreeChart chart;
            private ChartPanel chartPanel;

            public ModelListRenderer() {
                chart = ChartFactory.createXYLineChart("Random", "counts", "samples", null);
                chartPanel = new ChartPanel(chart, true, true, true, false, true) {
                    @Override
                    public Dimension getPreferredSize() {
                        return new Dimension(W, H);
                    }
                };
            }

            @Override
            public Component getListCellRendererComponent(
                JList modelList, XYSeriesCollection series, int index, boolean isSelected, boolean hasFocus) {
                XYPlot plot = chart.getXYPlot();
                plot.setDataset(series);
                return chartPanel;
            }
        }
    }
}

Answer 2

尝试只使用一个 JFreeChart 和一个 ChartPanel 并将其重用于您的渲染器。目前，您正在为每个单元格中的每个绘制请求创建一个新图表。

所以这些对象应该是你的类的成员对象，并且根据请求设置数据并返回chartPanel。

编辑：

这是一个例子。我不知道确切的方法签名，所以我只是将方法命名为“setData”：

static class ChartListRenderer implements ListCellRenderer<XYSeriesCollection> {

  private JFreeChart chart = ChartFactory.createXYLineChart("Random", "counts", "samples");
  private ChartPanel chartPanel = new ChartPanel(chart, true, true, true, false, true){
    @Override
    public Dimension getPreferredSize() {
      return new Dimension(W, H);}
  };

  @Override
  public Component getListCellRendererComponent(JList<? extends XYSeriesCollection> chartList, XYSeriesCollection serie, int index,
                                                boolean isSelected, boolean cellHasFocus) {
    chart.setData(serie);
    return chartPanel;
  }
}