当我尝试打印JLabel的图标时，我遇到了NullPointerException。 我想要的只是使用按钮将其打印在纸上。什么似乎是我的错误？这是我的代码：
package at;
import java.awt.Color;
import java.awt.Component;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Rectangle;
import java.awt.Toolkit;
import java.awt.image.BufferedImage;
import java.awt.print.PageFormat;
import java.awt.print.Paper;
import java.awt.print.Printable;
import java.awt.print.PrinterException;
import java.awt.print.PrinterJob;
import java.io.File;
import java.io.IOException;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.imageio.ImageIO;
import javax.swing.ImageIcon;
import javax.swing.JComponent;
import javax.swing.JLabel;
public class M extends javax.swing.JFrame {
/**
* Creates new form M
*/
public M() {
initComponents();
}
public static void printComponent(JComponent comp, boolean fill) throws PrinterException {
PrinterJob pjob = PrinterJob.getPrinterJob();
PageFormat pf = pjob.defaultPage();
pf.setOrientation(PageFormat.LANDSCAPE);
PageFormat postformat = pjob.pageDialog(pf);
if (pf != postformat) {
//Set print component
pjob.setPrintable(new ComponentPrinter(comp, fill), postformat);
if (pjob.printDialog()) {
pjob.print();
}
}
}
public static void printComponentToFile(Component comp, boolean fill) throws PrinterException {
Paper paper = new Paper();
paper.setSize(8.3 * 72, 11.7 * 72);
paper.setImageableArea(18, 18, 559, 783);
PageFormat pf = new PageFormat();
pf.setPaper(paper);
pf.setOrientation(PageFormat.LANDSCAPE);
BufferedImage img = new BufferedImage(
(int) Math.round(pf.getWidth()),
(int) Math.round(pf.getHeight()),
BufferedImage.TYPE_INT_RGB);
Graphics2D g2d = img.createGraphics();
g2d.setColor(Color.WHITE);
g2d.fill(new Rectangle(0, 0, img.getWidth(), img.getHeight()));
ComponentPrinter cp = new ComponentPrinter(comp, fill);
try {
cp.print(g2d, pf, 0);
} finally {
g2d.dispose();
}
try {
ImageIO.write(img, "jpg", new File("Page-" + (fill ? "Filled" : "") + ".jpg"));
} catch (IOException ex) {
ex.printStackTrace();
}
}
public static class ComponentPrinter implements Printable {
private Component comp;
private boolean fill;
public ComponentPrinter(Component comp, boolean fill) {
this.comp = comp;
this.fill = fill;
}
@Override
public int print(Graphics g, PageFormat format, int page_index) throws PrinterException {
if (page_index > 0) {
return Printable.NO_SUCH_PAGE;
}
Graphics2D g2 = (Graphics2D) g;
g2.translate(format.getImageableX(), format.getImageableY());
double width = (int) Math.floor(format.getImageableWidth());
double height = (int) Math.floor(format.getImageableHeight());
if (!fill) {
width = Math.min(width, comp.getPreferredSize().width);
height = Math.min(height, comp.getPreferredSize().height);
}
comp.setBounds(0, 0, (int) Math.floor(width), (int) Math.floor(height));
if (comp.getParent() == null) {
comp.addNotify();
}
comp.validate();
comp.doLayout();
comp.printAll(g2);
if (comp.getParent() != null) {
comp.removeNotify();
}
return Printable.PAGE_EXISTS;
}
}
/**
* 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">
private void initComponents() {
jButton1 = new javax.swing.JButton();
BtnBack = new javax.swing.JButton();
jLabel2 = new javax.swing.JLabel();
setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
setTitle("A");
setBackground(new java.awt.Color(255, 255, 255));
setIconImage(Toolkit.getDefaultToolkit().getImage(MappingScreen.class.getResource("/at/icon.jpg")));
getContentPane().setLayout(new org.netbeans.lib.awtextra.AbsoluteLayout());
jButton1.setText("PRINT");
jButton1.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
jButton1ActionPerformed(evt);
}
});
getContentPane().add(jButton1, new org.netbeans.lib.awtextra.AbsoluteConstraints(1150, 650, 90, 30));
BtnBack.setIcon(new javax.swing.ImageIcon(getClass().getResource("/adventureresort/back.png"))); // NOI18N
BtnBack.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
BtnBackActionPerformed(evt);
}
});
getContentPane().add(BtnBack, new org.netbeans.lib.awtextra.AbsoluteConstraints(20, 620, 80, -1));
jLabel2.setIcon(new javax.swing.ImageIcon(getClass().getResource("/at/mapp.jpg"))); // NOI18N
getContentPane().add(jLabel2, new org.netbeans.lib.awtextra.AbsoluteConstraints(0, 0, -1, -1));
pack();
}// </editor-fold>
private void BtnBackActionPerformed(java.awt.event.ActionEvent evt) {
Home home =new Home();
home.show();
dispose();
}
private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {
try {
printComponent(jLabel2, false);
} catch (PrinterException ex) {
Logger.getLogger(MappingScreen.class.getName()).log(Level.SEVERE, null, ex);
}
}
/**
* @param args the command line arguments
*/
public static void main(String args[]) {
try {
JLabel label = new JLabel(
"This is a test",
new ImageIcon("/at/mapp.jpg"),
JLabel.CENTER);
printComponentToFile(label, true);
printComponentToFile(label, false);
} catch (PrinterException exp) {
exp.printStackTrace();
}
/* Set the Nimbus look and feel */
//<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
/* If Nimbus (introduced in Java SE 6) is not available, stay with the default look and feel.
* For details see http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html
*/
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(M.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (InstantiationException ex) {
java.util.logging.Logger.getLogger(M.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (IllegalAccessException ex) {
java.util.logging.Logger.getLogger(M.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (javax.swing.UnsupportedLookAndFeelException ex) {
java.util.logging.Logger.getLogger(M.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 M().setVisible(true);
}
});
}
// Variables declaration - do not modify
private javax.swing.JButton BtnBack;
private javax.swing.JButton jButton1;
private javax.swing.JLabel jLabel2;
// End of variables declaration
}
请帮忙。我正在使用netbeans。我真的打印这个jLabel的图标来完成一个项目。
这是错误：
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at javax.swing.ImageIcon.<init>(ImageIcon.java:205)
at at.M.initComponents(M.java:162)
at at.M.<init>(M.java:39)
at at.M$3.run(M.java:231)
at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:251)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:733)
at java.awt.EventQueue.access$200(EventQueue.java:103)
at java.awt.EventQueue$3.run(EventQueue.java:694)
at java.awt.EventQueue$3.run(EventQueue.java:692)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:703)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:242)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:161)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:150)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:146)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:138)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:91)