Non riesco a passare un jTextArea ad un'altra classe

**playbasfa** · 13-05-2012, 13:14

Se ti riferisci al codice presente all'interno di NewJFrame questo è codice autogenerato da Netbeans in seguito alla creazione di un'interfaccia grafica con gli appositi strumenti messi a disposizione.

Attualmente compila e va tutto a buon fine con

codice:

public NewJFrame() {
        Server objS=new Server();
        initComponents();
        objS.passa(jTextArea1);
}

a runtime non appena nella classe Server si arriva al punto in cui c'è il comando

codice:

jTextArea.append("XXXX");

mi segnala il java.lang.NullPointerException.

Posto tutto il codice per completezza:

codice:

package chat_v1c;
import java.net.*;
import java.io.*;

public class Chat_v1c 
{
    public static void main(String[] args) throws InterruptedException 
    {
        Server objS=new Server();
        objS.start();
        NewJFrame objG=new NewJFrame();
        objG.setVisible(true);
    }
}

codice:

package chat_v1c;
import java.net.*;
import java.io.*;
public class Server extends Thread
{
    BufferedReader dalClient;
    PrintWriter alClient;
    javax.swing.JTextArea jTextArea;
    
    
    
    public void passa(javax.swing.JTextArea a)
    {
        this.jTextArea=a;
        
    }
    
    public Server(){}


    @Override
    public void run()
    {
        String text="";
        Socket clientSocket=null;
        ServerSocket serverSocket=null;
        try
        {
            serverSocket=new ServerSocket(5555);
            clientSocket = serverSocket.accept();
            dalClient=new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
            alClient = new PrintWriter(clientSocket.getOutputStream(), true);
            while(!text.equals("bye"))
            {
                text=dalClient.readLine();
                System.out.println("ECCOMI!");
                System.out.println(clientSocket.getInetAddress() + "Said: " + text + "\n");
                jTextArea.append(clientSocket.getInetAddress() + "Said: " + text + "\n");
            }
            alClient.print(clientSocket.getInetAddress()+ "Disconnected!");
            serverSocket.close();
            System.out.println("FFFUORII");
        }
        catch (IOException e)
        {
            e.printStackTrace();
        }
    }
}

codice:

package chat_v1c;
import java.net.*;
import java.io.*;

public class Client 
{
    
    Socket s1;
    PrintWriter alServer;
    BufferedReader dalServer;
    String text;
    //BufferedReader t = new BufferedReader(new InputStreamReader(System.in));

    
    
    public void connectToSocket()
    {
        
        try
        {
        
        s1 = new Socket ("169.254.100.208",5555);
        System.out.print("Connection with "+s1.getInetAddress()+" establised! \n");
        alServer= new PrintWriter(s1.getOutputStream(),true);
        dalServer = new BufferedReader(new InputStreamReader(s1.getInputStream()));
        }
        catch(IOException e)
        {
            System.out.println(e);
        }
    }
    
    
    
    
    public void sendToServer(String text)
    {
        
           this.text=text;
                
                alServer.println(text); 
    }
}

codice:

/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */
package chat_v1c;

/**
 *
 * @author fabrizio
 */
public class NewJFrame extends javax.swing.JFrame {

    /**
     * Creates new form NewJFrame
     */
    int i=0;
    
    
    Client objC=new Client();
    
    
    public NewJFrame() {
        Server objS=new Server();
        initComponents();
        objS.passa(jTextArea1);

    }

    /**
     * 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();
        jTextField1 = new javax.swing.JTextField();
        jScrollPane1 = new javax.swing.JScrollPane();
        jTextArea1 = new javax.swing.JTextArea();

        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);

        jButton1.setText("Send");
        jButton1.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                jButton1ActionPerformed(evt);
            }
        });

        jTextField1.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                jTextField1ActionPerformed(evt);
            }
        });

        jTextArea1.setColumns(20);
        jTextArea1.setRows(5);
        jScrollPane1.setViewportView(jTextArea1);

        org.jdesktop.layout.GroupLayout layout = new org.jdesktop.layout.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(org.jdesktop.layout.GroupLayout.LEADING)
            .add(layout.createSequentialGroup()
                .addContainerGap()
                .add(layout.createParallelGroup(org.jdesktop.layout.GroupLayout.LEADING)
                    .add(layout.createSequentialGroup()
                        .add(jScrollPane1, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE, 380, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE)
                        .add(0, 8, Short.MAX_VALUE))
                    .add(layout.createSequentialGroup()
                        .add(jTextField1)
                        .addPreferredGap(org.jdesktop.layout.LayoutStyle.RELATED)
                        .add(jButton1)))
                .addContainerGap())
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(org.jdesktop.layout.GroupLayout.LEADING)
            .add(layout.createSequentialGroup()
                .addContainerGap()
                .add(jScrollPane1, org.jdesktop.layout.GroupLayout.DEFAULT_SIZE, 186, Short.MAX_VALUE)
                .add(18, 18, 18)
                .add(layout.createParallelGroup(org.jdesktop.layout.GroupLayout.LEADING)
                    .add(org.jdesktop.layout.GroupLayout.TRAILING, layout.createSequentialGroup()
                        .add(jButton1)
                        .add(61, 61, 61))
                    .add(org.jdesktop.layout.GroupLayout.TRAILING, layout.createSequentialGroup()
                        .add(jTextField1, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE, 75, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE)
                        .addContainerGap())))
        );

        pack();
    }// </editor-fold>                        

    private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {                                         
        // TODO add your handling code here:
        if(i==0)
        {            
            //objS.pass(jTextArea1);
            objC.connectToSocket();
            objC.sendToServer(jTextField1.getText());
            i=i+1;   
        }
        else
        {
            objC.sendToServer(jTextField1.getText());
            
        }
        
    }                                        

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

    /**
     * @param args the command line arguments
     */
    public static void main(String args[]) {
        /*
         * 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/tu...feel/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(NewJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (InstantiationException ex) {
            java.util.logging.Logger.getLogger(NewJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (IllegalAccessException ex) {
            java.util.logging.Logger.getLogger(NewJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (javax.swing.UnsupportedLookAndFeelException ex) {
            java.util.logging.Logger.getLogger(NewJFrame.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 NewJFrame().setVisible(true);
            }
        });
    }
    // Variables declaration - do not modify                     
    private javax.swing.JButton jButton1;
    private javax.swing.JScrollPane jScrollPane1;
    private javax.swing.JTextArea jTextArea1;
    private javax.swing.JTextField jTextField1;
    // End of variables declaration                   
}

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