Java Swing, 2nd Edition

Implementing Your Own Icons

Here’s a class that implements the Icon interface and uses ovals as simple icons:

// OvalIcon.java
//
import javax.swing.*;
import java.awt.*;

// A simple icon implementation that draws ovals
public class OvalIcon implements Icon {

  private int width, height;

  public OvalIcon(int w, int h) {
    width = w;
    height = h;
  }

  public void paintIcon(Component c, Graphics g, int x, int y) {
    g.drawOval(x, y, width-1, height-1);
  }

  public int getIconWidth( ) { return width; }
  public int getIconHeight( ) { return height; }
}

A simple class that creates a few labels shows how it works:

// TestOval.java
//
import javax.swing.*;
import java.awt.*;

public class TestOval {
  public static void main(String[] args) {
    JFrame f = new JFrame( );
    f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    JLabel label1 = new JLabel(new OvalIcon(20,50));
    JLabel label2 = new JLabel(new OvalIcon(50,20));
    JLabel label3 = new JLabel("Round!", new OvalIcon(60,60), SwingConstants.CENTER);
    label3.setHorizontalTextPosition(SwingConstants.CENTER);

    Container c = f.getContentPane( );
    c.setLayout(new FlowLayout( ));
    c.add(label1);
    c.add(label2);
    c.add(label3);
    f.pack( );
    f.setVisible(true);
  }
}

Running this test program produces the display shown in Figure 4-7.

Figure 4-7. OvalIcon labels