如何打印预览JTable

Question

我是一个初级的Java开发人员，我想构建一个类，它在屏幕上使用一个JTable和预览，如何在默认打印机上打印它。这就是我们所谓的“打印预览”，就像MS Word，Excel等。

正如我们已经知道的，Java不支持这种现成的功能。

根据我在googling中找到的一些例子，我构建了两个类。第一个TestPreview.java只显示JTable，第二个PrintPreview.java预览如何在打印机上打印JTable。

我有两个按钮要查看页面，"PREV“、"NEXT”和“print”按钮来打印JTable。我的问题是，当我的JTable有太多行，跨多个页面时，PrintPreview就不能工作。它一次又一次地显示同一个页面。而且，它没有显示整个JTable数据，但只有一些，我也搞不清楚原因。

请帮帮忙。

下面是我的两堂课

TestPreview.java

package printpreviewdemo;

import javax.swing.*;
import java.awt.BorderLayout;
import java.awt.FlowLayout;
import java.awt.Frame;
import java.awt.event.*;
import java.awt.print.*;
import java.text.MessageFormat;
import javax.print.attribute.*;
import javax.print.attribute.standard.MediaPrintableArea;
import javax.print.attribute.standard.OrientationRequested;
import javax.print.attribute.standard.Sides;
import javax.swing.JTable.PrintMode;

class TestPreview extends JFrame implements ActionListener {
    PrinterJob printerJob = PrinterJob.getPrinterJob();
    HashPrintRequestAttributeSet attributes = new HashPrintRequestAttributeSet();
    JTable table = null;

    public TestPreview() {
        super("Test of Print Preview");
        getContentPane().add(createTable());
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
        setExtendedState(Frame.MAXIMIZED_BOTH);
        setVisible(true);
    }

    private JPanel createTable() {
       String val[][] = {
            {"A", "Test 01", "A", "Test 01"}, 
            {"B", "Test 02", "B", "Test 02"}, 
            {"C", "Test 03", "C", "Test 03"},
            {"D", "Test 04", "D", "Test 04"}, 
            {"E", "Test 05", "E", "Test 05"}, 
            {"F", "Test 06", "F", "Test 06"},
            {"G", "Test 01", "G", "Test 01"}, 
            {"H", "Test 02", "H", "Test 02"}, 
            {"I", "Test 03", "I", "Test 03"},
            {"J", "Test 03", "J", "Test 03"},
            {"K", "Test 04", "K", "Test 04"}, 
            {"L", "Test 05", "L", "Test 05"}, 
            {"M", "Test 06", "M", "Test 06"},
            {"N", "Test 01", "N", "Test 01"}, 
            {"O", "Test 02", "O", "Test 02"}, 
            {"P", "Test 03", "P", "Test 03"},
            {"Q", "Test 04", "Q", "Test 04"}, 
            {"R", "Test 05", "R", "Test 05"}, 
            {"S", "Test 06", "S", "Test 06"},
            {"T", "Test 01", "T", "Test 01"}, 
            {"U", "Test 02", "U", "Test 02"}, 
            {"V", "Test 03", "V", "Test 03"},
            {"W", "Test 04", "W", "Test 04"}, 
            {"X", "Test 05", "X", "Test 05"}, 
            {"Y", "Test 06", "Y", "Test 06"},
            {"Z", "Test 01", "Z", "Test 01"},
            {"1", "Test 02", "1", "Test 02"}, 
            {"2", "Test 03", "2", "Test 03"},
            {"3", "Test 04", "3", "Test 04"}, 
            {"4", "Test 05", "4", "Test 05"}, 
            {"5", "Test 06", "5", "Test 06"},
            {"6", "Test 01", "6", "Test 01"}, 
            {"7", "Test 02", "7", "Test 02"}, 
            {"8", "Test 03", "8", "Test 03"},
            {"9", "Test 04", "9", "Test 04"}, 
            {"10", "Test 05","10", "Test 05"},
            {"11", "Test 02","11", "Test 02"}, 
            {"12", "Test 03","12", "Test 03"},
            {"13", "Test 04","13", "Test 04"}, 
            {"14", "Test 05","14", "Test 05"}, 
            {"15", "Test 06","15", "Test 06"},
            {"16", "Test 01","16", "Test 01"}, 
            {"17", "Test 02","17", "Test 02"}, 
            {"18", "Test 03","18", "Test 03"},
            {"19", "Test 04","19", "Test 04"}, 
            {"20", "Test 05","20", "Test 05"},
            {"30", "Test 05","30", "Test 05"},
            {"31", "Test 02","31", "Test 02"}, 
            {"32", "Test 03","32", "Test 03"},
            {"33", "Test 04","33", "Test 04"}, 
            {"34", "Test 05","34", "Test 05"}, 
            {"35", "Test 06","35", "Test 06"},
            {"36", "Test 01","36", "Test 01"}, 
            {"37", "Test 02","37", "Test 02"}, 
            {"38", "Test 03","38", "Test 03"},
            {"39", "Test 04","39", "Test 04"}, 
            {"40", "Test 05","40", "Test 05"},
            {"40", "Test 05","40", "Test 05"},
            {"41", "Test 02","41", "Test 02"}, 
            {"42", "Test 03","42", "Test 03"},
            {"43", "Test 04","43", "Test 04"}, 
            {"44", "Test 05","44", "Test 05"}, 
            {"45", "Test 06","45", "Test 06"},
            {"46", "Test 01","46", "Test 01"}, 
            {"47", "Test 02","47", "Test 02"}, 
            {"48", "Test 03","48", "Test 03"},
            {"49", "Test 04","49", "Test 04"}, 
            {"50", "Test 05","50", "Test 05"},
            {"50", "Test 05","50", "Test 05"},
            {"51", "Test 02","51", "Test 02"}, 
            {"52", "Test 03","52", "Test 03"},
            {"53", "Test 04","53", "Test 04"}, 
            {"54", "Test 05","54", "Test 05"}, 
            {"55", "Test 06","55", "Test 06"},
            {"56", "Test 01","56", "Test 01"}, 
            {"57", "Test 02","57", "Test 02"}, 
            {"58", "Test 03","58", "Test 03"},
            {"59", "Test 04","59", "Test 04"}, 
            {"60", "Test 05","60", "Test 05"}
        };

        String headers[] = {"A", "B", "C", "D"};
        table = new JTable(val, headers);
        JButton previewButton = new JButton("Preview Table");
        previewButton.addActionListener(this);
        JPanel panel = new JPanel(new BorderLayout()), top = new JPanel(new FlowLayout());
        top.add(previewButton);
        panel.add(top, "North"); 
        panel.add(new JScrollPane(table), "Center");
        return panel;
    }

    @Override
    public void actionPerformed(ActionEvent ae) {
        if (ae.getActionCommand().equals("Preview Table"))
            attributes.add(new MediaPrintableArea(6, 6, 198, 278, MediaPrintableArea.MM)); // A4: 210x297mm
            attributes.add(Sides.DUPLEX);
            attributes.add(OrientationRequested.LANDSCAPE);
            new PrintPreview(
                table.getPrintable(PrintMode.FIT_WIDTH, null, new MessageFormat("Page {0}") ), 
                printerJob.getPageFormat(attributes)
            );
    }

    public static void main(String arg[]) {
        new TestPreview();
    }
}

PrintPreview.java

package printpreviewdemo;

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

class PrintPreview extends JFrame implements ActionListener, ItemListener {
    JButton printButton = new JButton("Print");
    Pageable pageable = null;
    double scale = 1.0;
    Page page[] = null;
    JComboBox combobox = new JComboBox();
    CardLayout cardlayout = new CardLayout();
    JPanel previewPanel = new JPanel(cardlayout);
    JButton backButton = new JButton("PREV"), forwardButton = new JButton("NEXT");

    public PrintPreview(final Printable printable, final PageFormat pageFormat) {
        super("Print Preview");        
        pageable = new Pageable() {
            @Override
            public int getNumberOfPages() {
                Graphics graphics = new BufferedImage(1, 1, BufferedImage.TYPE_INT_RGB).getGraphics();                
                int numPages = 0;
                try {
                    while (printable.print(graphics, pageFormat, numPages) == Printable.PAGE_EXISTS) {
                        numPages++;
                    }
                } catch (Exception ex) {
                }
                return numPages;
            }

            @Override
            public PageFormat getPageFormat(int x) {
                return pageFormat;
            }

            @Override
            public Printable getPrintable(int x) {
                return printable;
            }
        };
        createPreview();
    }

    private void createPreview() {
        page = new Page[pageable.getNumberOfPages()];
        PageFormat pageFormat = pageable.getPageFormat(0);
        Dimension size = new Dimension((int) pageFormat.getPaper().getWidth(), (int) pageFormat.getPaper().getHeight());
        if (pageFormat.getOrientation() != PageFormat.PORTRAIT) {
            size = new Dimension(size.height, size.width);
        }
        for (int i = 0; i < page.length; i++) {
            combobox.addItem("" + (i + 1));
            page[i] = new Page(i, size);
            previewPanel.add("" + (i + 1), new JScrollPane(page[i]));
        }
        setTopPanel();
        getContentPane().add(previewPanel, "Center");
        pack();
        setExtendedState(Frame.MAXIMIZED_BOTH);
        setVisible(true);
    }

    private void setTopPanel() {
        FlowLayout fl = new FlowLayout();
        GridBagLayout gbl = new GridBagLayout();

        JPanel topPanel = new JPanel(gbl), temp = new JPanel(fl);
        backButton.addActionListener(this);
        forwardButton.addActionListener(this);
        backButton.setEnabled(false);
        forwardButton.setEnabled(page.length > 1);

        temp.add(combobox);
        temp.add(backButton);
        temp.add(forwardButton);
        temp.add(printButton);

        topPanel.add(temp);
        printButton.addActionListener(this);
        combobox.addItemListener(this);
        getContentPane().add(topPanel, "North");
    }

    @Override
    public void itemStateChanged(ItemEvent ie) {
        cardlayout.show(previewPanel, (String) combobox.getSelectedItem());
        backButton.setEnabled(combobox.getSelectedIndex() == 0 ? false : true);
        forwardButton.setEnabled(combobox.getSelectedIndex() == combobox.getItemCount() - 1 ? false : true);
        validate();
    }

    @Override
    public void actionPerformed(ActionEvent ae) {
        Object o = ae.getSource();
        if (o == printButton) {
            try {
                PrinterJob pj = PrinterJob.getPrinterJob();
                pj.defaultPage(pageable.getPageFormat(0));
                pj.setPageable(pageable);
                if (pj.printDialog()) {
                    pj.print();
                }
            } catch (Exception ex) {
                JOptionPane.showMessageDialog(null, ex.toString(), "Error in Printing", 1);
            }
        } else if (o == backButton) {
            combobox.setSelectedIndex(combobox.getSelectedIndex() == 0 ? 0 : combobox.getSelectedIndex() - 1);
            if (combobox.getSelectedIndex() == 0) {
                backButton.setEnabled(false);
            }
        } else if (o == forwardButton) {
            combobox.setSelectedIndex(combobox.getSelectedIndex() == combobox.getItemCount() - 1 ? 0 : combobox.getSelectedIndex() + 1);
            if (combobox.getSelectedIndex() == combobox.getItemCount() - 1) {
                forwardButton.setEnabled(false);
            }
        }
    }

    class Page extends JLabel {
        final int n;
        final PageFormat pageformat;
        BufferedImage bufferimage = null;
        Dimension size = null;

        public Page(int currentpage, Dimension size) {
            this.size = size;
            bufferimage = new BufferedImage(size.width, size.height, BufferedImage.TYPE_INT_RGB);
            n = currentpage;
            pageformat = pageable.getPageFormat(n);
            Graphics g = bufferimage.getGraphics();
            g.setColor(Color.WHITE);                       
            g.fillRect(0, 0, (int) pageformat.getWidth(), (int) pageformat.getHeight());
            try {
                pageable.getPrintable(n).print(g, pageformat, n);
            } catch (Exception ex) {
            }
            setIcon(new ImageIcon(bufferimage));
        }
    }
}

Answer 1

怀疑它是否仍然令人感兴趣，但问题是TablePrintable是单一用途的。没有办法重新设置它的第二次。

第二次调用jTable.getPrintable()将获得一个新的TablePrintable，因此您需要使用第一个用于计数页面，第二个用于实际打印。

实际上，你不需要计算页数。getNumberofPages()可以返回零；只要结束打印循环，当它运行完页面。

另一种解决方法是复制TablePrintable的源，并为变量'last‘和矩形值添加一个重置方法。