nullpointerexception java代码

Question

我正在尝试使用netbeans中的电子邮件客户端发送电子邮件，但我的代码中出现空指针异常。这是我的代码（有三个类）：

EmailClient.java

package sendemail;

public class EmailClient extends javax.swing.JFrame {

    SendMail sm=new SendMail();
    Settings set=new Settings();
    public EmailClient() {
        initComponents();
    }


    @SuppressWarnings("unchecked")
    +Generated code                     

    private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {                                         
       // TODO add your handling code here:
        sm.setVisible(true);
    }                                        

    private void jButton2ActionPerformed(java.awt.event.ActionEvent evt) {                                         
        // TODO add your handling code here:
    }                                        

    private void jButton3ActionPerformed(java.awt.event.ActionEvent evt) {                                         
        // TODO add your handling code here:
    }                                        

    private void jMenuItem2ActionPerformed(java.awt.event.ActionEvent evt) {                                           
        // TODO add your handling code here:
        set.setVisible(true);
    }                                          

    public static void main(String args[]) {
        /* Create and display the form */
        java.awt.EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                new EmailClient().setVisible(true);
            }
        });
    }

    // Variables declaration - do not modify                     
    private javax.swing.JButton jButton1;
    private javax.swing.JButton jButton2;
    private javax.swing.JButton jButton3;
    private javax.swing.JLabel jLabel1;
    private javax.swing.JLabel jLabel2;
    private javax.swing.JLabel jLabel3;
    private javax.swing.JLabel jLabel4;
    private javax.swing.JLabel jLabel5;
    private javax.swing.JLabel jLabel6;
    private javax.swing.JMenu jMenu4;
    private javax.swing.JMenu jMenu5;
    private javax.swing.JMenuBar jMenuBar2;
    private javax.swing.JMenuItem jMenuItem2;
    private javax.swing.JPanel jPanel1;
    private javax.swing.JPanel jPanel3;
    private javax.swing.JPanel jPanel4;
    private javax.swing.JScrollPane jScrollPane1;
    private javax.swing.JTextArea jTextArea1;
    // End of variables declaration                   


}

Settings.java

package sendemail;
import javax.swing.*;
import java.awt.*;

public class Settings extends javax.swing.JFrame {

    public String uname;
    public String pass;
    public String smtpserver;
    public String  port;
    /**
     * Creates new form Settings
     */
    public Settings() {
        initComponents();
    }

    public String getUname() {
        return uname;
    }

    public String getPass() {
        return pass;
    }

    public String getSmtpserver() {
        return smtpserver;
    }

    public String getPort() {
        return port;
    }



    @SuppressWarnings("unchecked")
    +Generated Code                   

    private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {                                         
        // TODO add your handling code here:
       uname=jTextField1.getText().toString();
        pass=jPasswordField1.getPassword().toString();

        smtpserver=jComboBox1.getSelectedItem().toString();
        port=jComboBox2.getSelectedItem().toString();

        if(uname.equals("") || pass.equals("") || smtpserver.equals("") || port.equals("") )
    {
            JOptionPane.showMessageDialog(this,"All Fields are mandatory");
    }                                        
    else
        {
            setVisible(false);
        }

    }                                        

    private void jComboBox1ActionPerformed(java.awt.event.ActionEvent evt) {                                           
        // TODO add your handling code here:
    }                                          

    public static void main(String args[]) {
        /* Create and display the form */
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                new Settings().setVisible(false);
            }
        });
    }

    // Variables declaration - do not modify                     
    private javax.swing.JButton jButton1;
    private javax.swing.JComboBox jComboBox1;
    private javax.swing.JComboBox jComboBox2;
    private javax.swing.JLabel jLabel1;
    private javax.swing.JLabel jLabel2;
    private javax.swing.JLabel jLabel3;
    private javax.swing.JLabel jLabel4;
    private javax.swing.JPanel jPanel1;
    private javax.swing.JPasswordField jPasswordField1;
    private javax.swing.JTextField jTextField1;
    // End of variables declaration                   
    jTextField1=new JTextField();
}

SendMail.Java

package sendemail;

import java.util.Properties;
import javax.mail.Message;
import javax.mail.Session;
import javax.mail.Transport;
import javax.mail.internet.InternetAddress;
import javax.mail.internet.MimeMessage;
import javax.swing.JOptionPane;
import java.awt.*;
import javax.mail.*;
import javax.mail.MessagingException;


public class SendMail extends javax.swing.JFrame {

    Settings setfrm=new Settings();
    String subject;
    String from;

    public SendMail() {
        initComponents();
    }


    @SuppressWarnings("unchecked")
    +Generated Code                    

    private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {                                         
        // TODO add your handling code here:
        try
        {
        final String user=setfrm.getUname();
        final String password=setfrm.getPass();
        String portnum=setfrm.getPort();
        String smtpname=setfrm.getSmtpserver();
        String to=jTextField1.getText();
        subject=jTextField2.getText();
        Properties properties=new Properties();
        properties.put("mail.smtp.host",smtpname.toString());
        properties.put("mail.smtp.socketFactory.port",portnum.toString());
        properties.put("mail.smtp.socketFactory.class","javax.net.ssl.SSLSocketFactory");
        properties.put("mail.smtp.port",portnum.toString());
        properties.put("mail.smtp.auth","true");
        Session session=Session.getDefaultInstance(properties,
           new javax.mail.Authenticator() {
               protected PasswordAuthentication getPasswordAuthentication(){
                return new PasswordAuthentication(user,password);

           }

           }

           );
        MimeMessage message=new MimeMessage(session);
        message.setFrom(new InternetAddress(user));
        message.setRecipients(Message.RecipientType.TO, InternetAddress.parse(jTextField1.getText().toString()));
        message.setSubject(subject);
        message.setText(jTextArea1.getText());
        Transport.send(message);
        JOptionPane.showMessageDialog(null,"message sent");
        }
        catch(MessagingException mex)
        {
            JOptionPane.showMessageDialog(null,mex);
        }
    }                                        

    private void jButton2ActionPerformed(java.awt.event.ActionEvent evt) {                                         
        // TODO add your handling code here:
    }                                        

    private void jTextField1ActionPerformed(java.awt.event.ActionEvent evt) {                                            
        // TODO add your handling code here:
    }                                           

    public static void main(String args[]) {
        /* Create and display the form */
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                new SendMail().setVisible(true);
            }
        });
    }

    // Variables declaration - do not modify                     
    private javax.swing.JButton jButton1;
    private javax.swing.JButton jButton2;
    private javax.swing.JLabel jLabel1;
    private javax.swing.JLabel jLabel2;
    private javax.swing.JPanel jPanel1;
    private javax.swing.JScrollPane jScrollPane1;
    private javax.swing.JTextArea jTextArea1;
    private javax.swing.JTextField jTextField1;
    private javax.swing.JTextField jTextField2;
    // End of variables declaration                   
    jTextField1=new JTextField();
    jTextField2=new JTextField();
}

我正在尝试使用SendMail.java发送电子邮件，同时从Settings.java输入发件人的电子邮件和密码，而EmailClient.java仅用于在点击按钮时将JFrames可见性设置为true或false。 / p>

错误：

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
    at sendemail.SendMail.jButton1ActionPerformed(SendMail.java:157)
    at sendemail.SendMail.access$100(SendMail.java:24)
    at sendemail.SendMail$2.actionPerformed(SendMail.java:76)
    at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2018)
    at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2341)
    at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402)
    at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259)
    at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:252)
    at java.awt.Component.processMouseEvent(Component.java:6505)
    at javax.swing.JComponent.processMouseEvent(JComponent.java:3311)
    at java.awt.Component.processEvent(Component.java:6270)
    at java.awt.Container.processEvent(Container.java:2229)
    at java.awt.Component.dispatchEventImpl(Component.java:4861)
    at java.awt.Container.dispatchEventImpl(Container.java:2287)
    at java.awt.Component.dispatchEvent(Component.java:4687)
    at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4832)
    at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4492)
    at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4422)
    at java.awt.Container.dispatchEventImpl(Container.java:2273)
    at java.awt.Window.dispatchEventImpl(Window.java:2719)
    at java.awt.Component.dispatchEvent(Component.java:4687)
    at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:735)
    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.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:87)
    at java.awt.EventQueue$4.run(EventQueue.java:708)
    at java.awt.EventQueue$4.run(EventQueue.java:706)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
    at java.awt.EventQueue.dispatchEvent(EventQueue.java:705)
    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)

Answer 1

jTextField1为null，您需要像

一样初始化它

JTextField jTextField1 = new JTextField();

我还看到所有成员字段都没有正确初始化。您需要确保在对它们调用任何方法调用之前初始化所有实例成员字段