Background

• The importance of turning off double buffering globally, not just for the top-level component.
• The fact that you can write a general-purpose printComponent routine to which you can pass any component you want printed. The component to be printed need not have a print method, implement any particular interface, or in fact do anything special at all. In fact, if you don't really care to understand how printing works behind the scenes, you can skip reading this tutorial and simply download PrintUtilities.java and call PrintUtilities.printComponent(componentToBePrinted) whenever you want to print the contents of a window.

Printing Basics

1. Setting Up the Print Job
   This is virtually always done the same way: get a PrinterJob object, pass a Printable to its setPrintable method, call printDialog to pop up an OS-specific print dialog, and finally, assuming the user hasn't cancelled the printing from the dialog (you check this by testing the return value of printDialog), call print on the PrinterJob.

   Note that the role of the Printable is to define a print method showing how the actual drawing to the printer will be done. That's described in the next section.

   Here's an example:

       PrinterJob printJob = PrinterJob.getPrinterJob();
       printJob.setPrintable(this);
       if (printJob.printDialog())
         try { 
           printJob.print();
         } catch(PrinterException pe) {
           System.out.println("Error printing: " + pe);
         }

   Here's a representative sample of what you see when you call printDialog:
2. Rendering Graphics on the Printer
   The Printable that is passed to setPrintable must have a print method that describes how to send drawing to the printer.

   In general, the first step is to decide what to do for different pages of your print job, since Java repeatedly calls print with higher and higher page indexes until print returns NO_SUCH_PAGE. In the specific case of printing Swing components, however, you only have a single page. So you return PAGE_EXISTS for index 0, NO_SUCH_PAGE otherwise.

   The second step is to start drawing. In general, you can do any sort of drawing you want. In the specific case of printing Swing components, however, your drawing should just be a high-resolution version of what the component looks like on the screen. So you cast the Graphics object to Graphics2D, scale the resolution to the printer, and call the component's paint method with this scaled Graphics2D. Note that it is this reliance on the Graphics2D's coordinate transformations that prevents this capability from being available in the Java 1.1 version of Swing. For more details on Graphics2D, please see my separate Java2D tutorial.

   Here's an example:

         public int print(Graphics g, PageFormat pageFormat, int pageIndex) {
           if (pageIndex > 0) {
             return(NO_SUCH_PAGE);
           } else {
             Graphics2D g2d = (Graphics2D)g;
             g2d.translate(pageFormat.getImageableX(), pageFormat.getImageableY());
             // Turn off double buffering
             componentToBePrinted.paint(g2d);
             // Turn double buffering back on
             return(PAGE_EXISTS);
           }
         }
         

The Role of Double Buffering

Consequently, you need to make sure double buffering is turned off before you print. If you have only a single JPanel or other JComponent, you can call setDoubleBuffered(false) on it before calling the paint method, and setDoubleBuffered(true) afterwards. However, this suffers from the flaw that if you later nest another container inside, you're right back where you started from. A much better solution is to globally turn off double buffering via

RepaintManager currentManager = 
  RepaintManager.currentManager(c);
currentManager.setDoubleBufferingEnabled(false);

A General-Purpose Component-Printing Routine

PrintUtilities.java (Download source code)

import java.awt.*;
import javax.swing.*;
import java.awt.print.*;

public class PrintUtilities implements Printable {
  private Component componentToBePrinted;

  public static void printComponent(Component c) {
    new PrintUtilities(c).print();
  }
  
  public PrintUtilities(Component componentToBePrinted) {
    this.componentToBePrinted = componentToBePrinted;
  }
  
  public void print() {
    PrinterJob printJob = PrinterJob.getPrinterJob();
    printJob.setPrintable(this);
    if (printJob.printDialog())
      try {
        printJob.print();
      } catch(PrinterException pe) {
        System.out.println("Error printing: " + pe);
      }
  }

  public int print(Graphics g, PageFormat pageFormat, int pageIndex) {
    if (pageIndex > 0) {
      return(NO_SUCH_PAGE);
    } else {
      Graphics2D g2d = (Graphics2D)g;
      g2d.translate(pageFormat.getImageableX(), pageFormat.getImageableY());
      disableDoubleBuffering(componentToBePrinted);
      componentToBePrinted.paint(g2d);
      enableDoubleBuffering(componentToBePrinted);
      return(PAGE_EXISTS);
    }
  }

  public static void disableDoubleBuffering(Component c) {
    RepaintManager currentManager = RepaintManager.currentManager(c);
    currentManager.setDoubleBufferingEnabled(false);
  }

  public static void enableDoubleBuffering(Component c) {
    RepaintManager currentManager = RepaintManager.currentManager(c);
    currentManager.setDoubleBufferingEnabled(true);
  }
}

Printing in Java: An Example

PrintExample Result

PrintExample.java (Download source code)

import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
import java.awt.print.*;

public class PrintExample extends JFrame
                          implements ActionListener {
  public static void main(String[] args) {
    new PrintExample();
  }

  public PrintExample() {
    super("Printing Swing Components");
    WindowUtilities.setNativeLookAndFeel();
    addWindowListener(new ExitListener());
    Container content = getContentPane();
    JButton printButton = new JButton("Print");
    printButton.addActionListener(this);
    JPanel buttonPanel = new JPanel();
    buttonPanel.setBackground(Color.white);
    buttonPanel.add(printButton);
    content.add(buttonPanel, BorderLayout.SOUTH);
    DrawingPanel drawingPanel = new DrawingPanel();
    content.add(drawingPanel, BorderLayout.CENTER);
    pack();
    setVisible(true);
  }

  public void actionPerformed(ActionEvent event) {
    PrintUtilities.printComponent(this);
  }
}

DrawingPanel.java (Download source code)

import java.awt.*;
import javax.swing.*;
import java.awt.geom.*;

public class DrawingPanel extends JPanel {
  private int fontSize = 90;
  private String message = "Java 2D";
  private int messageWidth;
  
  public DrawingPanel() {
    setBackground(Color.white);
    Font font = new Font("Serif", Font.PLAIN, fontSize);
    setFont(font);
    FontMetrics metrics = getFontMetrics(font);
    messageWidth = metrics.stringWidth(message);
    int width = messageWidth*5/3;
    int height = fontSize*3;
    setPreferredSize(new Dimension(width, height));
  }

  public void paintComponent(Graphics g) {
    super.paintComponent(g);
    Graphics2D g2d = (Graphics2D)g;
    int x = messageWidth/10;
    int y = fontSize*5/2;
    g2d.translate(x, y);
    g2d.setPaint(Color.lightGray);
    AffineTransform origTransform = g2d.getTransform();
    g2d.shear(-0.95, 0);
    g2d.scale(1, 3);
    g2d.drawString(message, 0, 0);
    g2d.setTransform(origTransform);
    g2d.setPaint(Color.black);
    g2d.drawString(message, 0, 0);
  }
}