Java Swing How to - Extend ListCellRenderer to display icons

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Question

We would like to know how to extend ListCellRenderer to display icons.

Answer

/* w  w w.jav a  2 s  .c o  m*/
/*
Definitive Guide to Swing for Java 2, Second Edition
By John Zukowski     
ISBN: 1-893115-78-X
Publisher: APress
*/

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Component;
import java.awt.Container;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.Polygon;

import javax.swing.DefaultListCellRenderer;
import javax.swing.Icon;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JList;
import javax.swing.JScrollPane;
import javax.swing.ListCellRenderer;

public class ComplexRenderingSample {
  public static void main(String args[]) {

    Object elements[][] = {
        { new Font("Helvetica", Font.PLAIN, 20), Color.red,
            new DiamondIcon(Color.blue), "Help" },
        { new Font("TimesRoman", Font.BOLD, 14), Color.blue,
            new DiamondIcon(Color.green), "Me" },
        { new Font("Courier", Font.ITALIC, 18), Color.green,
            new DiamondIcon(Color.black), "I'm" },
        { new Font("Helvetica", Font.BOLD | Font.ITALIC, 12),
            Color.gray, new DiamondIcon(Color.magenta), "Trapped" },
        { new Font("TimesRoman", Font.PLAIN, 32), Color.pink,
            new DiamondIcon(Color.yellow), "Inside" },
        { new Font("Courier", Font.BOLD, 16), Color.yellow,
            new DiamondIcon(Color.red), "This" },
        { new Font("Helvetica", Font.ITALIC, 8), Color.darkGray,
            new DiamondIcon(Color.pink), "Computer" } };

    JFrame frame = new JFrame("Complex Renderer");
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    Container contentPane = frame.getContentPane();

    JList jlist = new JList(elements);
    ListCellRenderer renderer = new ComplexCellRenderer();
    jlist.setCellRenderer(renderer);
    JScrollPane scrollPane = new JScrollPane(jlist);
    contentPane.add(scrollPane, BorderLayout.CENTER);

    JComboBox comboBox = new JComboBox(elements);
    comboBox.setRenderer(renderer);
    contentPane.add(comboBox, BorderLayout.NORTH);

    frame.setSize(300, 300);
    frame.setVisible(true);
  }
}

class DiamondIcon implements Icon {
  private Color color;

  private boolean selected;

  private int width;

  private int height;

  private Polygon poly;

  private static final int DEFAULT_WIDTH = 10;

  private static final int DEFAULT_HEIGHT = 10;

  public DiamondIcon(Color color) {
    this(color, true, DEFAULT_WIDTH, DEFAULT_HEIGHT);
  }

  public DiamondIcon(Color color, boolean selected) {
    this(color, selected, DEFAULT_WIDTH, DEFAULT_HEIGHT);
  }

  public DiamondIcon(Color color, boolean selected, int width, int height) {
    this.color = color;
    this.selected = selected;
    this.width = width;
    this.height = height;
    initPolygon();
  }

  private void initPolygon() {
    poly = new Polygon();
    int halfWidth = width / 2;
    int halfHeight = height / 2;
    poly.addPoint(0, halfHeight);
    poly.addPoint(halfWidth, 0);
    poly.addPoint(width, halfHeight);
    poly.addPoint(halfWidth, height);
  }

  public int getIconHeight() {
    return height;
  }

  public int getIconWidth() {
    return width;
  }

  public void paintIcon(Component c, Graphics g, int x, int y) {
    g.setColor(color);
    g.translate(x, y);
    if (selected) {
      g.fillPolygon(poly);
    } else {
      g.drawPolygon(poly);
    }
    g.translate(-x, -y);
  }
}

class ComplexCellRenderer implements ListCellRenderer {
  protected DefaultListCellRenderer defaultRenderer = new DefaultListCellRenderer();

  public Component getListCellRendererComponent(JList list, Object value,
      int index, boolean isSelected, boolean cellHasFocus) {
    Font theFont = null;
    Color theForeground = null;
    Icon theIcon = null;
    String theText = null;

    JLabel renderer = (JLabel) defaultRenderer
        .getListCellRendererComponent(list, value, index, isSelected,
            cellHasFocus);

    if (value instanceof Object[]) {
      Object values[] = (Object[]) value;
      theFont = (Font) values[0];
      theForeground = (Color) values[1];
      theIcon = (Icon) values[2];
      theText = (String) values[3];
    } else {
      theFont = list.getFont();
      theForeground = list.getForeground();
      theText = "";
    }
    if (!isSelected) {
      renderer.setForeground(theForeground);
    }
    if (theIcon != null) {
      renderer.setIcon(theIcon);
    }
    renderer.setText(theText);
    renderer.setFont(theFont);
    return renderer;
  }
}

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