Java打印功能全解析

# Java 打印功能全解析 ## 1. 打印功能的发展历程 早期的 Java 开发工具包完全不支持打印功能，小程序无法进行打印操作，若要在应用程序中实现打印，需借助第三方库。SDK 1.1 引入了轻量级的打印支持，能实现简单的打印输出，但打印质量有限。其打印模型旨在让浏览器厂商打印小程序在网页上的显示内容，不过未得到广泛应用。 SDK 1.2 开启了与 2D 图形深度集成的强大打印模型，SDK 1.3 进行了小幅度改进，而 SDK 1.4 则带来了重要增强，如发现打印机特性和支持服务器端打印管理的流式打印作业。 ## 2. 打印 2D 图形 ### 2.1 基本要求 要生成打印输出，需完成以下两个关键步骤： - 提供一个实现 `Printable` 接口的对象。 - 启动打印作业。 `Printable` 接口仅有一个方法： ```java int print(Graphics g, PageFormat format, int page) ``` 此方法在打印引擎需要对页面进行打印格式设置时被调用。在该方法中，需将需要打印的文本和图像绘制到图形上下文中。`PageFormat` 参数提供纸张大小和打印边距信息，`page` 参数指明要渲染的页面编号。 ### 2.2 启动打印作业 使用 `PrinterJob` 类启动打印作业，具体步骤如下： 1. 调用静态方法 `getPrinterJob` 获取打印作业对象。 2. 设置要打印的 `Printable` 对象。 示例代码如下： ```java Printable canvas = ...; PrinterJob job = PrinterJob.getPrinterJob(); job.setPrintable(canvas); ``` ### 2.3 打印对话框 在启动打印作业前，建议调用 `printDialog` 方法显示打印对话框，让用户选择打印机、打印页面范围及其他打印设置。示例代码如下： ```java HashPrintRequestAttributeSet attributes = new HashPrintRequestAttributeSet(); if (job.printDialog(attributes)) { try { job.print(); } catch (PrinterException exception) { // 处理异常 } } ``` ### 2.4 页面格式 `PageFormat` 类提供了关于打印页面的详细信息，如纸张大小、可打印区域的尺寸和位置等。相关方法如下： - `getWidth()` 和 `getHeight()`：返回纸张的宽度和高度，单位为点（1 点等于 1/72 英寸）。 - `getImageableWidth()` 和 `getImageableHeight()`：返回可打印区域的宽度和高度。 - `getImageableX()` 和 `getImageableY()`：返回可打印区域左上角的坐标。 ### 2.5 示例代码 以下是一个完整的示例，展示如何在屏幕和打印页面上渲染相同的图形： ```java import java.awt.*; import java.awt.event.*; import java.awt.font.*; import java.awt.geom.*; import java.awt.print.*; import java.util.*; import javax.print.*; import javax.print.attribute.*; import javax.swing.*; public class PrintTest { public static void main(String[] args) { JFrame frame = new PrintTestFrame(); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); frame.show(); } } class PrintTestFrame extends JFrame { public PrintTestFrame() { setTitle("PrintTest"); setSize(300, 300); Container contentPane = getContentPane(); PrintPanel canvas = new PrintPanel(); contentPane.add(canvas, BorderLayout.CENTER); PrintRequestAttributeSet attributes = new HashPrintRequestAttributeSet(); JPanel buttonPanel = new JPanel(); JButton printButton = new JButton("Print"); buttonPanel.add(printButton); printButton.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent event) { try { PrinterJob job = PrinterJob.getPrinterJob(); job.setPrintable(canvas); if (job.printDialog(attributes)) { job.print(attributes); } } catch (PrinterException exception) { JOptionPane.showMessageDialog(PrintTestFrame.this, exception); } } }); JButton pageSetupButton = new JButton("Page setup"); buttonPanel.add(pageSetupButton); pageSetupButton.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent event) { PrinterJob job = PrinterJob.getPrinterJob(); job.pageDialog(attributes); } }); contentPane.add(buttonPanel, BorderLayout.NORTH); } } class PrintPanel extends JPanel implements Printable { public void paintComponent(Graphics g) { super.paintComponent(g); Graphics2D g2 = (Graphics2D) g; drawPage(g2); } public int print(Graphics g, PageFormat pf, int page) throws PrinterException { if (page >= 1) return Printable.NO_SUCH_PAGE; Graphics2D g2 = (Graphics2D) g; g2.translate(pf.getImageableX(), pf.getImageableY()); g2.draw(new Rectangle2D.Double(0, 0, pf.getImageableWidth(), pf.getImageableHeight())); drawPage(g2); return Printable.PAGE_EXISTS; } public void drawPage(Graphics2D g2) { FontRenderContext context = g2.getFontRenderContext(); Font f = new Font("Serif", Font.PLAIN, 72); GeneralPath clipShape = new GeneralPath(); TextLayout layout = new TextLayout("Hello", f, context); AffineTransform transform = AffineTransform.getTranslateInstance(0, 72); Shape outline = layout.getOutline(transform); clipShape.append(outline, false); layout = new TextLayout("World", f, context); transform = AffineTransform.getTranslateInstance(0, 144); outline = layout.getOutline(transform); clipShape.append(outline, false); g2.draw(clipShape); g2.clip(clipShape); final int NLINES = 50; Point2D p = new Point2D.Double(0, 0); for (int i = 0; i < NLINES; i++) { double x = (2 * getWidth() * i) / NLINES; double y = (2 * getHeight() * (NLINES - 1 - i)) / NLINES; Point2D q = new Point2D.Double(x, y); g2.draw(new Line2D.Double(p, q)); } } } ``` ### 2.6 使用本地打印对话框 在 SDK 1.4 之前，打印系统使用主机平台的本地打印和页面设置对话框。显示本地打印对话框，可调用无参数的 `printDialog` 方法；显示本地页面设置对话框，需将默认的 `PageFormat` 对象传递给 `pageDialog` 方法。 ## 3. 多页打印 实际应用中，通常不直接将 `Printable` 对象传递给打印作业，而是使用实现 `Pageable` 接口的对象，Java 平台提供了 `Book` 类。`Book` 由多个 `Printable` 部分组成，可通过添加 `Printable` 对象及其页面数量来创建。 示例代码如下： ```java Book book = new Book(); Printable coverPage = ...; Printable bodyPages = ...; book.append(coverPage, pageFormat); // 追加 1 页 book.append(bodyPages, pageFormat, pageCount); PrinterJob printJob = PrinterJob.getPrinterJob(); printJob.setPageable(book); ``` 使用 `Book` 类的挑战在于，打印前需明确每个部分的页面数量，因此 `Printable` 类需要一个布局算法来计算打印页面上内容的布局。同时，要考虑用户更改页面格式的情况，若发生更改，需重新计算布局。 以下是一个多页打印的示例代码： ```java import java.awt.*; import java.awt.event.*; import java.awt.font.*; import java.awt.geom.*; import java.awt.print.*; import java.util.*; import javax.print.*; import javax.print.attribute.*; import javax.swing.*; public class BookTest { public static void main(String[] args) { JFrame frame = new BookTestFrame(); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); frame.show(); } } class BookTestFrame extends JFrame { private JTextField text; private PageFormat pageFormat; private PrintRequestAttributeSet attributes; private static final int WIDTH = 300; private static final int HEIGHT = 100; public BookTestFrame() { setTitle("BookTest"); setSize(WIDTH, HEIGHT); Container contentPane = getContentPane(); text = new JTextField(); contentPane.add(text, BorderLayout.NORTH); attributes = new HashPrintRequestAttributeSet(); JPanel buttonPanel = new JPanel(); JButton printButton = new JButton("Print"); buttonPanel.add(printButton); printButton.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent event) { try { PrinterJob job = PrinterJob.getPrinterJob(); job.setPageable(makeBook()); if (job.printDialog(attributes)) { job.print(attributes); } } catch (PrinterException exception) { JOptionPane.showMessageDialog(BookTestFrame.this, exception); } } }); JButton pageSetupButton = new JButton("Page setup"); buttonPanel.add(pageSetupButton); pageSetupButton.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent event) { PrinterJob job = PrinterJob.getPrinterJob(); pageFormat = job.pageDialog(attributes); } }); JButton printPreviewButton = new JButton("Print preview"); buttonPanel.add(printPreviewButton); printPreviewButton.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent event) { PrintPreviewDialog dialog = new PrintPreviewDialog(makeBook()); dialog.show(); } }); contentPane.add(buttonPanel, BorderLayout.SOUTH); } public Book makeBook() { if (pageFormat == null) { PrinterJob job = PrinterJob.getPrinterJob(); pageFormat = job.defaultPage(); } Book book = new Book(); String message = text.getText(); Banner banner = new Banner(message); int pageCount = banner.getPageCount((Graphics2D) getGraphics(), pageFormat); book.append(new CoverPage(message + " (" + pageCount + " pages)"), pageFormat); book.append(banner, pageFormat, pageCount); return book; } } class Banner implements Printable { private String message; private double scale; public Banner(String m) { message = m; } public int getPageCount(Graphics2D g2, PageFormat pf) { if (message.equals("")) return 0; FontRenderContext context = g2.getFontRenderContext(); Font f = new Font("Serif", Font.PLAIN, 72); Rectangle2D bounds = f.getStringBounds(message, context); scale = pf.getImageableHeight() / bounds.getHeight(); double width = scale * bounds.getWidth(); int pages = (int) Math.ceil(width / pf.getImageableWidth()); return pages; } public int print(Graphics g, PageFormat pf, int page) throws PrinterException { Graphics2D g2 = (Graphics2D) g; if (page > getPageCount(g2, pf)) return Printable.NO_SUCH_PAGE; g2.translate(pf.getImageableX(), pf.getImageableY()); drawPage(g2, pf, page); return Printable.PAGE_EXISTS; } public void drawPage(Graphics2D g2, PageFormat pf, int page) { if (message.equals("")) return; page--; // 考虑封面页 drawCropMarks(g2, pf); g2.clip(new Rectangle2D.Double(0, 0, pf.getImageableWidth(), pf.getImageableHeight())); g2.translate(-page * pf.getImageableWidth(), 0); g2.scale(scale, scale); FontRenderContext context = g2.getFontRenderContext(); Font f = new Font("Serif", Font.PLAIN, 72); TextLayout layout = new TextLayout(message, f ```