Java打印和打印预览机制

import java.awt.BasicStroke;
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Component;
import java.awt.Dimension;
import java.awt.Font;
import java.awt.FontMetrics;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.print.PageFormat;
import java.awt.print.Printable;
import java.awt.print.PrinterException;
import java.awt.print.PrinterJob;

import javax.swing.JButton;
import javax.swing.JDialog;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.SwingUtilities;
import javax.swing.WindowConstants;
import javax.swing.text.BadLocationException;
import javax.swing.text.Document;

/**
 * 使用了原始的分页方式去渲染JTextArea，提供了打印预览机制。
 * <p>
 * 事实上，我们还可以通过其他方式打印JTextArea：
 * <ol>
 * <li>{@code Component.print(Graphics g);} or
 * {@code Component.printAll(Graphics g);}</li>
 * <li>{@code Component.paint(Graphics g);} or
 * {@code Component.paintAll(Graphics g);} whose rending may be slightly
 * different to the previous method (for example, <code>JFrame</code>)</li>
 * <li>{@code JTable.print();} or {@code JTextComponent.print();} provide
 * especially powerful and convenient printing mechanism</li>
 * </ol>
 * 
 * @author Gaowen
 */
public class PrintUIComponent extends JPanel implements ActionListener,
		Printable {
	private static final long serialVersionUID = 4797002827940419724L;
	private static JFrame frame;
	private JTextArea textAreaToPrint;
	private PrinterJob job;
	private int[] pageBreaks;// array of page break line positions
	private String[] textLines;
	private Header header;

	public PrintUIComponent() {
		super(new BorderLayout());
		textAreaToPrint = new JTextArea(50, 20);
		for (int i = 1; i <= 50; i++) {
			textAreaToPrint.append("Line " + i + "\n");
		}
		JScrollPane scrollPane = new JScrollPane(textAreaToPrint);
		scrollPane.setPreferredSize(new Dimension(250, 200));
		add(scrollPane, BorderLayout.CENTER);
		JButton printButton = new JButton("Print This TextArea");
		printButton.setName("printButton");
		printButton.addActionListener(this);
		JButton printPreviewButton = new JButton("Print Preview");
		printPreviewButton.setName("printPreviewButton");
		printPreviewButton.addActionListener(this);
		JPanel buttonGroup = new JPanel(new GridLayout(2, 1));
		buttonGroup.add(printButton);
		buttonGroup.add(printPreviewButton);
		add(buttonGroup, BorderLayout.SOUTH);

		/* Initialize PrinterJob */
		initPrinterJob();
	}

	public static void main(String[] args) {
		SwingUtilities.invokeLater(new Runnable() {
			@Override
			public void run() {
				createAndShowGUI();
			}
		});
	}

	private static void createAndShowGUI() {
		frame = new JFrame("Print UI Example");
		frame.setContentPane(new PrintUIComponent());
		frame.pack();
		frame.setLocationRelativeTo(null);
		frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
		frame.setVisible(true);
	}

	private void initTextLines() {
		Document doc = textAreaToPrint.getDocument();
		try {
			String text = doc.getText(0, doc.getLength());
			textLines = text.split("\n");
		} catch (BadLocationException e) {
			e.printStackTrace();
		}
	}

	private void initPrinterJob() {
		job = PrinterJob.getPrinterJob();
		job.setJobName("Print TextArea");// 出现在系统打印任务列表
		job.setPrintable(this);
	}

	@Override
	public int print(Graphics graphics, PageFormat pageFormat, int pageIndex)
			throws PrinterException {
		/*
		 * It is safe to use a copy of this graphics as this will not involve
		 * changes to it.
		 */
		Graphics2D g2 = (Graphics2D) graphics.create();

		/* Calculate "pageBreaks" */
		Font font = new Font("Serif", Font.PLAIN, 12);
		FontMetrics metrics = g2.getFontMetrics(font);
		int lineHeight = metrics.getHeight();
		if (pageBreaks == null) {
			initTextLines();
			int linesPerPage = (int) (pageFormat.getImageableHeight() / lineHeight);
			int numBreaks = (textLines.length - 1) / linesPerPage;
			pageBreaks = new int[numBreaks];
			for (int b = 0; b < numBreaks; b++) {
				pageBreaks[b] = (b + 1) * linesPerPage;
			}
		}

		/* Condition to exit printing */
		if (pageIndex > pageBreaks.length) {
			return NO_SUCH_PAGE;
		}

		/* (0,0) is outside the imageable area, translate to avoid clipping */
		g2.translate(pageFormat.getImageableX(), pageFormat.getImageableY());

		/* Draw each line that is on this page */
		int y = 0;
		int start = (pageIndex == 0) ? 0 : pageBreaks[pageIndex - 1];
		int end = (pageIndex == pageBreaks.length) ? textLines.length
				: pageBreaks[pageIndex];
		for (int line = start; line < end; line++) {
			y += lineHeight;
			g2.drawString(textLines[line], 0, y);
		}

		/* dispose of the graphics copy */
		g2.dispose();

		/* Tell the caller that this page is part of the printed document */
		return PAGE_EXISTS;
	}

	@Override
	public void actionPerformed(ActionEvent e) {
		Object actionEventSource = e.getSource();
		if (actionEventSource instanceof JButton) {
			JButton button = (JButton) actionEventSource;
			if (button.getName().equals("printButton")) {
				pageBreaks = null;// reset pagination
				boolean ok = job.printDialog();
				if (ok) {
					try {
						job.print();
					} catch (PrinterException ex) {
						/* The job did not successfully complete */
						ex.printStackTrace();
					}
				}
			} else if (button.getName().equals("printPreviewButton")) {
				pageBreaks = null;// reset pagination
				createAndShowPreviewDialog();
			}
		}
	}

	private void createAndShowPreviewDialog() {
		JDialog previewDialog = new JDialog(frame, "Print Preview Dialog", true);
		JPanel contentPane = new JPanel(new BorderLayout());
		PreviewArea previewArea = new PreviewArea();
		previewArea.addMouseListener(new PreviewAreaMouseAdapter(previewArea));
		JScrollPane scrollPane = new JScrollPane(previewArea);
		contentPane.add(scrollPane, BorderLayout.CENTER);
		header = new Header(previewArea);
		contentPane.add(header, BorderLayout.NORTH);
		previewDialog.setContentPane(contentPane);
		previewDialog.setSize(600, 600);
		previewDialog
				.setDefaultCloseOperation(WindowConstants.DISPOSE_ON_CLOSE);
		previewDialog.setVisible(true);
	}

	private class Header extends Component {
		private static final long serialVersionUID = -1741188309769027249L;
		private PreviewArea previewArea;
		private boolean paintable;

		private Header(PreviewArea previewArea) {
			this.previewArea = previewArea;
		}

		private void setPaintable(boolean paintable) {
			this.paintable = paintable;
		}

		@Override
		public void paint(Graphics g) {
			if (paintable) {
				g.setColor(Color.GRAY);
				g.drawString(
						String.valueOf(previewArea.getPageIndex() + 1)
								+ "/"
								+ String.valueOf(pageBreaks.length + 1)
								+ " pages (Click left mouse button to preview next page; right to previous)",
						10, 15);
			}
		}

		@Override
		public Dimension getPreferredSize() {
			return new Dimension(super.getPreferredSize().width, 20);
		}
	}

	private class PreviewArea extends Component {
		private static final long serialVersionUID = -6384174997251439843L;
		private PageFormat pageFormat;
		private int pageIndex;
		private int w;
		private int h;
		private final int marginX = 10;
		private final int marginY = 20;

		private PreviewArea() {
			pageFormat = job.pageDialog(job.defaultPage());
			pageIndex = 0;
			w = (int) pageFormat.getWidth();
			h = (int) pageFormat.getHeight();
		}

		private int getPageIndex() {
			return pageIndex;
		}

		private void setPageIndex(int pageIndex) {
			this.pageIndex = pageIndex;
		}

		@Override
		public Dimension getPreferredSize() {
			return new Dimension(w + 2 * marginX, h + 2 * marginY);
		}

		@Override
		public void paint(Graphics g) {
			Graphics2D g2 = (Graphics2D) g.create();
			g2.translate(marginX, marginY);
			g2.drawRect(0, 0, w, h);
			int ix = (int) (pageFormat.getImageableX() - 1);
			int iy = (int) (pageFormat.getImageableY() - 1);
			int iw = (int) (pageFormat.getImageableWidth() + 1);
			int ih = (int) (pageFormat.getImageableHeight() + 1);
			g2.setStroke(new BasicStroke(1f, BasicStroke.CAP_ROUND,
					BasicStroke.JOIN_ROUND, 10f, new float[] { 5, 5 }, 0f));
			g2.drawRect(ix, iy, iw, ih);
			try {
				PrintUIComponent.this.print(g2, pageFormat, pageIndex);
			} catch (PrinterException e) {
				e.printStackTrace();
			}
			g2.dispose();
			header.setPaintable(true);
			header.repaint();
		}
	}

	private class PreviewAreaMouseAdapter extends MouseAdapter {
		private PreviewArea previewArea;

		private PreviewAreaMouseAdapter(PreviewArea previewArea) {
			this.previewArea = previewArea;
		}

		@Override
		public void mouseClicked(MouseEvent e) {
			int currentIndex = previewArea.getPageIndex();
			if (e.getButton() == MouseEvent.BUTTON1) {
				/* next page */
				if (currentIndex < pageBreaks.length) {
					previewArea.setPageIndex(currentIndex + 1);
					previewArea.repaint();
				}
			} else if (e.getButton() == MouseEvent.BUTTON3) {
				/* previous page */
				if (currentIndex > 0) {
					previewArea.setPageIndex(currentIndex - 1);
					previewArea.repaint();
				}
			}
		}
	}
}