writing output to a textarea in a different class instead of using system.out.println

Question

I have a GUI class called readGUI and a listener class called TopicS

The aim is to print the output from TopicS in a textArea which is located in readGUI

I am not sure how to do this but I tried to append textarea ie.

in GUI class I added

     public void receiveMsg (String s)
    { jTextArea1.append(s);
    }

while in listner classs Topics I added the two lines after the commented out System.out.printlm(messageText)

 public void onMessage(Message message)
 {
  try
  {
   String messageText = null;
   if (message instanceof TextMessage)
    messageText = ((TextMessage)message).getText();
  // System.out.println(messageText);
readGUI rm = readGUI();
rm.receiveMsg(messageText);
  }
  catch (JMSException e)
  {
   e.printStackTrace();
  }
 }

The Listner prints message that are published to the correct topic's, but instead of on the console I would like to put results on GUI I called from

The two full classes are below if it helps readGUI

    public class readGUI extends javax.swing.JFrame {

    /** Creates new form readMessages */
    public readGUI() {
        initComponents();
    }

    /** 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() {

        jLabel1 = new javax.swing.JLabel();
        topicCombobox = new javax.swing.JComboBox();
        jScrollPane1 = new javax.swing.JScrollPane();
        jTextArea1 = new javax.swing.JTextArea();
        jLabel2 = new javax.swing.JLabel();
        listenme = new javax.swing.JButton();
        jButton2 = new javax.swing.JButton();
        jScrollPane2 = new javax.swing.JScrollPane();
        jTextArea2 = new javax.swing.JTextArea();
        jComboBox2 = new javax.swing.JComboBox();
        jComboBox3 = new javax.swing.JComboBox();
        jLabel3 = new javax.swing.JLabel();
        jLabel4 = new javax.swing.JLabel();

        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);

        jLabel1.setFont(new java.awt.Font("Tahoma", 1, 14));
        jLabel1.setText("Listen for specific messages");
        // String [] tlist = { "topic1", "WGB1", "WGB2", "Item 4" };
        topicCombobox.setModel(new javax.swing.DefaultComboBoxModel(new String[] { "topic1", "WGB1", "WGB2", "Item 4" }));

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

        jLabel2.setText("Location:");

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

        jButton2.setText("Get complete log");
        jButton2.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                jButton2ActionPerformed(evt);
            }
        });

        jTextArea2.setColumns(20);
        jTextArea2.setRows(5);
        jScrollPane2.setViewportView(jTextArea2);

        jComboBox2.setModel(new javax.swing.DefaultComboBoxModel(new String[] { "Item 1", "Item 2", "Item 3", "Item 4" }));

        jComboBox3.setModel(new javax.swing.DefaultComboBoxModel(new String[] { "Item 1", "Item 2", "Item 3", "Item 4" }));

        jLabel3.setFont(new java.awt.Font("Tahoma", 0, 14)); // NOI18N
        jLabel3.setText("Sensor");

        jLabel4.setFont(new java.awt.Font("Tahoma", 0, 14)); // NOI18N
        jLabel4.setText("Location");

        javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addGap(71, 71, 71)
                .addComponent(jLabel2)
                .addGap(30, 30, 30)
                .addComponent(topicCombobox, javax.swing.GroupLayout.PREFERRED_SIZE, 129, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, 81, Short.MAX_VALUE)
                .addComponent(listenme, javax.swing.GroupLayout.PREFERRED_SIZE, 246, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addGap(46, 46, 46))
            .addGroup(layout.createSequentialGroup()
                .addGap(219, 219, 219)
                .addComponent(jLabel1)
                .addContainerGap(239, Short.MAX_VALUE))
            .addGroup(layout.createSequentialGroup()
                .addGap(19, 19, 19)
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                    .addGroup(javax.swing.GroupLayout.Alignment.TRAILING, layout.createSequentialGroup()
                        .addGap(22, 22, 22)
                        .addComponent(jLabel4, javax.swing.GroupLayout.PREFERRED_SIZE, 66, javax.swing.GroupLayout.PREFERRED_SIZE)
                        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
                        .addComponent(jComboBox3, javax.swing.GroupLayout.PREFERRED_SIZE, 102, javax.swing.GroupLayout.PREFERRED_SIZE)
                        .addGap(44, 44, 44)
                        .addComponent(jLabel3, javax.swing.GroupLayout.PREFERRED_SIZE, 60, javax.swing.GroupLayout.PREFERRED_SIZE)
                        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, 50, Short.MAX_VALUE)
                        .addComponent(jComboBox2, javax.swing.GroupLayout.PREFERRED_SIZE, 83, javax.swing.GroupLayout.PREFERRED_SIZE)
                        .addGap(32, 32, 32)
                        .addComponent(jButton2, javax.swing.GroupLayout.PREFERRED_SIZE, 127, javax.swing.GroupLayout.PREFERRED_SIZE)
                        .addGap(32, 32, 32))
                    .addGroup(layout.createSequentialGroup()
                        .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.TRAILING)
                            .addComponent(jScrollPane2, javax.swing.GroupLayout.Alignment.LEADING, javax.swing.GroupLayout.DEFAULT_SIZE, 609, Short.MAX_VALUE)
                            .addComponent(jScrollPane1, javax.swing.GroupLayout.Alignment.LEADING, javax.swing.GroupLayout.PREFERRED_SIZE, 609, javax.swing.GroupLayout.PREFERRED_SIZE))
                        .addContainerGap(19, Short.MAX_VALUE))))
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addContainerGap()
                .addComponent(jLabel1)
                .addGap(11, 11, 11)
                .addComponent(jScrollPane1, javax.swing.GroupLayout.PREFERRED_SIZE, 100, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(jLabel2)
                    .addComponent(listenme)
                    .addComponent(topicCombobox, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
                .addComponent(jScrollPane2, javax.swing.GroupLayout.PREFERRED_SIZE, 106, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addGap(18, 18, 18)
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(jButton2)
                    .addComponent(jComboBox2, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addComponent(jComboBox3, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addComponent(jLabel4)
                    .addComponent(jLabel3))
                .addContainerGap(31, Short.MAX_VALUE))
        );

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

    private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {                                         
        System.out.println("test test test"); 
        System.out.print("you pressed" +topicCombobox.getSelectedItem());
        //TopicPublish tp = new TopicPublish();
       TopicS a = new TopicS();
 a.addTopicToListner((String) topicCombobox.getSelectedItem());
//int i = topicCombobox.getSelectedIndex();
//a.addTopicToListner(tlist[i]);
    }                                        

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

    /**
    * @param args the command line arguments
    */
    public static void main(String args[]) {
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                new readGUI().setVisible(true);
            }
        });

}
    public void receiveMsg (String s)
{jTextArea1.append(s);
}
    // Variables declaration - do not modify
    private javax.swing.JButton listenme;
    private javax.swing.JButton jButton2;
    private javax.swing.JComboBox topicCombobox;
    private javax.swing.JComboBox jComboBox2;
    private javax.swing.JComboBox jComboBox3;
    private javax.swing.JLabel jLabel1;
    private javax.swing.JLabel jLabel2;
    private javax.swing.JLabel jLabel3;
    private javax.swing.JLabel jLabel4;
    private javax.swing.JScrollPane jScrollPane1;
    private javax.swing.JScrollPane jScrollPane2;
    private javax.swing.JTextArea jTextArea1;
    private javax.swing.JTextArea jTextArea2;
    // End of variables declaration

}

TopicS

import java.util.Hashtable;

import javax.jms.JMSException;
import javax.jms.Message;
import javax.jms.MessageListener;
import javax.jms.Session;
import javax.jms.TextMessage;
import javax.jms.Topic;
import javax.jms.TopicConnection;
import javax.jms.TopicConnectionFactory;
import javax.jms.TopicSession;
import javax.jms.TopicSubscriber;
import javax.naming.Context;
import javax.naming.InitialContext;
import javax.naming.NamingException;

public class TopicS implements MessageListener
{

 private TopicConnection topicConnection;
 private TopicSession topicSession;
 public Topic topic;
 private TopicSubscriber topicSubscriber;


 public TopicS()
            {}
            public void addTopicToListner(String t){
  try
  {
   // create a JNDI context
   Hashtable properties = new Hashtable();
   properties.put(Context.INITIAL_CONTEXT_FACTORY,"org.exolab.jms.jndi.InitialContextFactory");
   properties.put(Context.PROVIDER_URL,"rmi://localhost:1099/");
   Context context = new InitialContext(properties);

   // retrieve topic connection factory
   TopicConnectionFactory topicConnectionFactory = 
       (TopicConnectionFactory)context.lookup("JmsTopicConnectionFactory");
   // create a topic connection
   topicConnection = topicConnectionFactory.createTopicConnection();

   // create a topic session
   // set transactions to false and set auto acknowledgement of receipt of messages
   topicSession = topicConnection.createTopicSession(false,Session.AUTO_ACKNOWLEDGE);

   // retrieve topic
   topic = (Topic) context.lookup(t);

   // create a topic subscriber and associate to the retrieved topic
   topicSubscriber = topicSession.createSubscriber(topic);

   // associate message listener
   topicSubscriber.setMessageListener(this);

   // start delivery of incoming messages
   topicConnection.start();
  }
  catch (NamingException e)
  {
   e.printStackTrace();
  }
  catch (JMSException e)
  {
   e.printStackTrace();
  }
 } 

/* public static void main(String[] args)
 //{

  try
  {
   TopicS listener = new TopicS();
   Thread.currentThread().sleep(2000);
  }

  catch (InterruptedException e)
  {
   e.printStackTrace();
  }
 }
 */
 // process incoming topic messages
 public void onMessage(Message message)
 {
  try
  {
   String messageText = null;
   if (message instanceof TextMessage)
    messageText = ((TextMessage)message).getText();
  // System.out.println(messageText);
readGUI rm = readGUI();
rm.receiveMsg(messageText);
  }
  catch (JMSException e)
  {
   e.printStackTrace();
  }
 }
}

possible duplicate of [How to redirect console content to a textArea in java?](http://stackoverflow.com/questions/5107629/how-to-redirect-console-content-to-a-textarea-in-java) — trashgod, Mar 24 '11 at 00:04

score 1 · Answer 1 · answered Mar 24 '11 at 00:33

1

If you are appending text to a component and that work is being done NOT on the gui thread you will have problems. That appears to be what you are doing here. Use

SwingUtilities.invokeLater(new Runnable() {
    public void run() {
         rm.receiveMsg(messageText);
    }
});

so that that work is done on the gui thread.

I am also wondering what you are doing with this:

readGUI rm = readGUI();

it seems like you are trying to call a constructor without creating an object or something.

answered Mar 24 '11 at 00:33

MeBigFatGuy

28,272
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Where does the code you added go? in the gui class / listner Also, the readGUI rm = readGUI() was used with the idea that I could send outputted text to the readGUI 's JtextArea1 I also called {jTextArea1.append(s); in readGUI so maybe I'm misunderstanding the first line of text you wrote I am grateful for your reply but am still not 100% sure how to proceed, thanks – skal Mar 24 '11 at 00:51
Some piece of code has probably already created an instance of the readGUI class, and is showing the window. So the TopicS instance needs to reference that particular instance of the readGUI class. So you should change your TopicS constructor to take an instance of readGUI and store the reference in a member variable. Then when you want to populate the field, reference that field. – MeBigFatGuy Mar 24 '11 at 03:01

writing output to a textarea in a different class instead of using system.out.println

1 Answers1