pdfrender实现简易版pdf阅读器-支持鼠标拖动浏览

基于pdfrender实现简易版pdf阅读器，支持鼠标上下拖动实现翻页和滚动条支持

看了代码就知道其中的奥妙

PDFComponent类：

import com.sun.pdfview.PDFFile;import com.sun.pdfview.PDFPage;import com.sun.pdfview.PDFRenderer;import javax.swing.*;import java.awt.*;import java.awt.event.MouseAdapter;import java.awt.event.MouseEvent;import java.awt.print.PageFormat;import java.awt.print.Paper;import java.io.BufferedInputStream;import java.io.ByteArrayOutputStream;import java.io.FileInputStream;import java.nio.ByteBuffer;/** * pdf显示component * @author yy */public class PDFComponent extends JScrollPane {    private static final long serialVersionUID = 1L;    // byte array containing the PDF file content    //当前文件字符数组    private byte[] bytes = null;    //文件名称    private String fileName;    //每页高度（当前高度会根据当前窗体大小计算相对高度）    private double pageHeight;    //页面总高度（画布）    private double totalHeight;    //当前pdf文件    private PDFFile pdfFile;    //当前所查看的页数    private int index = 0;    /**     * y轴上一个值，鼠标按下时触发，鼠标释放时设置为0     */    private int preY = 0;    /**     * pdf组件     */    private JPanel pdfPanel;    public PDFComponent() {        pdfPanel = new JPanel(){            @Override            public void paintComponent(Graphics g) {                super.paintComponent(g);                //绘制当前页和下一页，避免滑动到两页中间位置出现文档显示不全问题（这样也解决了当文档太大时加载整个文档所消耗不必要的时间）                draw(g, index);                draw(g, index+1);            }        };        initComponents();    }    public PDFComponent(String fileName) {        this();        this.fileName = fileName;        readFile();    }    /**     * 初始化组件     */    private void initComponents(){        this.setViewportView(pdfPanel);        //添加滚动事件        this.getVerticalScrollBar().addAdjustmentListener((e)->{            int value = e.getValue();            PDFComponent.this.setIndex((int) (value / PDFComponent.this.getPageHeight() + 1));            PDFComponent.this.repaint();        });        pdfPanel.addMouseListener(new MouseAdapter() {            @Override            public void mousePressed(MouseEvent e) {                preY = e.getYOnScreen();            }            @Override            public void mouseReleased(MouseEvent e) {                preY = 0;            }        });        pdfPanel.addMouseMotionListener(new MouseAdapter() {            @Override            public void mouseDragged(MouseEvent e) {                if(preY == 0){//正常情况不会执行到当前方法快                    preY = e.getYOnScreen();                    return;                }                int currentY = e.getYOnScreen();                int tmpY = getVerticalScrollBar().getValue();                //如果拖动上一个值和当前值相等就直接返回                if(currentY == preY){                    return;                }                if( currentY > preY){                    tmpY -= 50;                }else if(currentY < preY){                    tmpY += 50;                }                getVerticalScrollBar().setValue(tmpY);                preY = currentY;            }        });    }    /**     * 读取当前文件     */    public void readFile() {        try (BufferedInputStream inputStream = new BufferedInputStream(new FileInputStream(fileName));) {            ByteArrayOutputStream outputStream = new ByteArrayOutputStream();            int b;            while ((b = inputStream.read()) != -1) {                outputStream.write(b);            }            this.bytes = outputStream.toByteArray();            pdfFile = new PDFFile(ByteBuffer.wrap(this.bytes));        } catch (Exception e) {            e.printStackTrace();        }    }    /**     * 改变当前component高度     */    public void changeHeight(){        totalHeight = pageHeight * pdfFile.getNumPages();        Dimension dimension = this.getSize();        dimension.setSize(dimension.getWidth(), totalHeight);        pdfPanel.setMinimumSize(dimension);        pdfPanel.setPreferredSize(dimension);        pdfPanel.setMaximumSize(dimension);        pdfPanel.setSize(dimension);    }    /**     * 绘制指定页数     * @param g     * @param pageIndex 页码     */    public void draw(Graphics g, int pageIndex) {        /**         * 如果当前文件或绘制下标超过pdf页数就不绘制         */        if(pdfFile == null || pageIndex > pdfFile.getNumPages()){            return;        }        PDFPage page = pdfFile.getPage(pageIndex);        Paper paper = new Paper();        int formatOrientation = page.getAspectRatio() > 1 ? PageFormat.LANDSCAPE                : PageFormat.PORTRAIT;        if (formatOrientation == PageFormat.LANDSCAPE) {            paper.setSize(page.getHeight(), page.getWidth());        } else {            paper.setSize(page.getWidth(), page.getHeight());        }        PageFormat pageFormat = new PageFormat();        pageFormat.setPaper(paper);        pageFormat.setOrientation(formatOrientation);        Graphics2D g2d = (Graphics2D) g.create();        //计算界面宽度与文档宽度的比例        double tmp = this.getSize().getWidth() / page.getWidth();        //重新计算高度（避免pdf变形）        pageHeight = pageFormat.getHeight() * tmp;        //重新设置panel高度        changeHeight();        //绘制到指定位置        Rectangle imgbounds = new Rectangle(0, (int)((pageIndex - 1) * pageHeight), (int)this.getSize().getWidth(),                (int)pageHeight);        PDFRenderer renderer = new PDFRenderer(page, g2d, imgbounds, null, Color.WHITE);        try {            page.waitForFinish();        } catch (InterruptedException e) {            // some exception handling            e.printStackTrace();        }        renderer.run();    }    public void setFileName(String fileName) {        this.fileName = fileName;    }    public double getPageHeight() {        return pageHeight;    }    public void setIndex(int index) {        this.index = index;    }}

MyJFrame：

import java.awt.event.AdjustmentEvent;import java.awt.event.AdjustmentListener;/** * @author Administrator */public class MyJFrame extends javax.swing.JFrame {    private int num = 1;    /**     * Creates new form MyJFrame     */    public MyJFrame() {        initComponents();        pDFComponent1.setFileName("C:\\Users\\Administrator\\Desktop\\*.pdf");        pDFComponent1.readFile();    }    /**     * This method is called from within the constructor to initialize the form.     * WARNING: Do NOT modify this code. The content of this method is always     * regenerated by the Form Editor.     */    @SuppressWarnings("unchecked")    // <editor-fold defaultstate="collapsed" desc="Generated Code">//GEN-BEGIN:initComponents    private void initComponents() {        pDFComponent1 = new PDFComponent();        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);        setMinimumSize(new java.awt.Dimension(806, 518));        getContentPane().add(pDFComponent1, java.awt.BorderLayout.CENTER);        pack();    }// </editor-fold>//GEN-END:initComponents    /**     * @param args the command line arguments     */    public static void main(String args[]) {        try {            for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {                if ("Nimbus".equals(info.getName())) {                    javax.swing.UIManager.setLookAndFeel(info.getClassName());                    break;                }            }        } catch (ClassNotFoundException ex) {            java.util.logging.Logger.getLogger(MyJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);        } catch (InstantiationException ex) {            java.util.logging.Logger.getLogger(MyJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);        } catch (IllegalAccessException ex) {            java.util.logging.Logger.getLogger(MyJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);        } catch (javax.swing.UnsupportedLookAndFeelException ex) {            java.util.logging.Logger.getLogger(MyJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);        }        //</editor-fold>        /* Create and display the form */        java.awt.EventQueue.invokeLater(new Runnable() {            public void run() {                new MyJFrame().setVisible(true);            }        });    }}

jar包就自己download（可直接在maven repository下载），我用的是：pdfrenderer-0.9.1-patched.jar。