public Object getValue() 
{
    return functionValue;
}

Return the last generated Image.

 public  void pageCanceled(ReportEvent event) 
{
    functionValue = null;
}

Receives notification that a page was canceled by the ReportProcessor. This method is called, when a page was removed from the report after it was generated.

 public  void pageFinished(ReportEvent event) 
{

}

Receives notification that a page is completed.

 public  void pageStarted(ReportEvent event) 
{
    final BufferedImage image = new BufferedImage(150, 50, BufferedImage.TYPE_INT_ARGB);
    final Graphics2D g2 = image.createGraphics();
    final JButton bt = new JButton("A Button");
    bt.setSize(90, 20);
    final JRadioButton radio = new JRadioButton("A radio button");
    radio.setSize(100, 20);
    g2.setColor(Color.darkGray);
    bt.paint(g2);
    g2.setColor(Color.blue);
    g2.setTransform(AffineTransform.getTranslateInstance(20, 20));
    radio.paint(g2);
    g2.setTransform(AffineTransform.getTranslateInstance(0, 0));
    g2.setPaint(Color.green);
    g2.setFont(new Font("Serif", Font.PLAIN, 10));
    g2.drawString("You are viewing a graphics of JFreeReport on index "
        + event.getState().getCurrentDisplayItem(), 10, 10);
    functionValue = new ImageReference(image);
}

Create a image according to the current state, simple and silly ...