Dynamic jTextArea

[coderX]

I'm trying to retrieve data from mysql table into a jTextArea. When I insert a data into the the table I want it to appear in the textarea without having to use a refresh button,so that it gets updated automatically while the program is running.
Here is what I tried:

         private void jButton2ActionPerformed(java.awt.event.ActionEvent evt) {
           int i,a;
           i=1;
           a=100;
           while(i<=a){ // <--- Loop for repeating the function
               try {
            conn = DriverManager.getConnection("jdbc:mysql://localhost/", "root" ,"db");
            String SQL = "SELECT * FROM table  " ;
            st = conn.createStatement();
      	    rset = st.executeQuery(SQL);
           
           
           while (rset.next()){
               
                jTextArea1.append(rset.getString("Info"));
              
           
           }
          
        }
        catch(Exception e) {
            System.out.println("Error");
        }
           } 
}

But when I use a loop,the program freezes and the UI becomes unresponsive.
Can someone help me in making the above function(retrieving data from database) repeat itself in regular intervals without a loop,so that the UI doesnt go unresponsive?

[Lionlev]

You should probably use threads
implements Runnable
and add run() method, inside of the run create a while loop that will do the same as refresh button.

[coderX]

You should probably use threads
implements Runnable
and add run() method, inside of the run create a while loop that will do the same as refresh button.

I dont know what threads,implements runnable are,but does it go like this?

class NewThread implements Runnable {
         public void run() {
             //code for refresh button
         }
     }

[JBelg]

Yup, that's how it works.

[coderX]

Since I'm using NetBeans I have no idea where to put thread and implements runnable,can someone tell me where to put it?here is the whole code:

import java.sql.*;
import javax.swing.JOptionPane;




public class Main extends javax.swing.JFrame {
    Connection conn = null;
    Statement st,s = null;
    
    ResultSet rset = null;
    ResultSet rs =null;
    /**
     * Creates new form Main
     */
   
     public  MainGUI() {
        initComponents();
        
        
    }
    
    
          
        @SuppressWarnings("unchecked")
    
    private void initComponents() {

        jPanel2 = new javax.swing.JPanel();
        jComboBox1 = new javax.swing.JComboBox();
        jScrollPane2 = new javax.swing.JScrollPane();
        jTextArea2 = new javax.swing.JTextArea();
        jScrollPane3 = new javax.swing.JScrollPane();
        jList1 = new javax.swing.JList();
        jButton1 = new javax.swing.JButton();
        jLabel1 = new javax.swing.JLabel();
        jLabel2 = new javax.swing.JLabel();
        jLabel3 = new javax.swing.JLabel();
        jCheckBox1 = new javax.swing.JCheckBox();
        jScrollPane1 = new javax.swing.JScrollPane();
        jTextArea1 = new javax.swing.JTextArea();
        jButton2 = new javax.swing.JButton();

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

      
    }
 
    private void jCheckBox1ActionPerformed(java.awt.event.ActionEvent evt) {
        // TODO add your handling code here:
           
        
    }//GEN-LAST:event_jCheckBox1ActionPerformed

    private void jComboBox1ActionPerformed(java.awt.event.ActionEvent evt) {
        // TODO add your handling code here:
    }
    private void jButton2ActionPerformed(java.awt.event.ActionEvent evt) {
        // TODO add your handling code here:
       // <-----------------------------------------------REFRESH BUTTON CODE
        
    }

        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(MainGUI.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (InstantiationException ex) {
            java.util.logging.Logger.getLogger(MainGUI.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (IllegalAccessException ex) {
            java.util.logging.Logger.getLogger(MainGUI.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (javax.swing.UnsupportedLookAndFeelException ex) {
            java.util.logging.Logger.getLogger(MainGUI.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        }
       

        /*
         * Create and display the form
         */
        java.awt.EventQueue.invokeLater(new Runnable() {

            @Override
            public void run() {
                new Main().setVisible(true);
                
            }
        });
        
    }
    // Variables declaration - do not modify//GEN-BEGIN:variables
    private javax.swing.JButton jButton1;
    private javax.swing.JButton jButton2;
    private javax.swing.JCheckBox jCheckBox1;
    private javax.swing.JComboBox jComboBox1;
    private javax.swing.JLabel jLabel1;
    private javax.swing.JLabel jLabel2;
    private javax.swing.JLabel jLabel3;
    private javax.swing.JList jList1;
    private javax.swing.JPanel jPanel2;
    private javax.swing.JScrollPane jScrollPane1;
    private javax.swing.JScrollPane jScrollPane2;
    private javax.swing.JScrollPane jScrollPane3;
    private javax.swing.JTextArea jTextArea1;
    private javax.swing.JTextArea jTextArea2;
    // End of variables declaration//GEN-END:variables
}

[Lionlev]

Since I'm using NetBeans I have no idea where to put thread and implements runnable,can someone tell me where to put it?here is the whole code:

public class Main extends javax.swing.JFrame {

public class Main extends javax.swing.JFrame implements Runnable

Since you don't know much about threads you must start the thread
Create another method:

public void blabla(){
		new Thread(this).start();
}

at the main method you should add:

Main lol = new Main();
lol.blabla();

That's basically it.
Inside the Run method you should add the infinite while loop:
while(true){
}
and inside of that loop you add functions which you want to repeat until the program closes.

Hope I was understandable xD
:D

[coderX]

It didnt work,does the run method go inside this?

public class MainGUI extends javax.swing.JFrame implements Runnable {

[SJF]

It didnt work,does the run method go inside this?

public class MainGUI extends javax.swing.JFrame implements Runnable {

Yes. Anything that implements Runnable MUST have a run() method that overrides the Interface Runnable's abstract public void run().

In English: Runnable contains a method run that is not implemented. If you say your class is a Runnable class it has to implement the unimplemented method!

[coderX]

Thank you guys so much its working fine now,but how do you stop the jtextarea from [bold]scrolling up[/bold] every time it refresh's?

[JBelg]

Getting JScrollPane to stop auto-scrolling

That post might help you out.

[coderX]

That didnt help man,since I'm using a loop to refresh the jTextArea ,it keeps going up continuously . Then I tried putting this into the loop:

 jTextArea1.setCaretPosition(jTextArea1.getText().length() - 1);

But now it keeps scrolling down and I'm not able to scroll freely.I want it to refresh in such a way that it doesn't affect the scroll.

[DarrylBurke]

Check out camickr's article on Text Area Scrolling « Java Tips Weblog

db

[coderX]

So should I use this?

 DefaultCaret caret = (DefaultCaret)textArea.getCaret();
caret.setUpdatePolicy(DefaultCaret.NEVER_UPDATE);

But where do I put this code,since NetBeans is creating most of the code,idk where.

[coderX]

This is what I did,but still it keeps going up,what am I doing wrong here?

  public void run() {
         
            int i=1;
            int a=100;
            DefaultCaret caret = (DefaultCaret)jTextArea1.getCaret();
            caret.setUpdatePolicy(DefaultCaret.NEVER_UPDATE);
            while (i<=a){
              
              //Code for refreshing

                
           
           }

[DarrylBurke]

To get better help sooner, post your latest attempt in the form of a SSCCE (Short, Self Contained, Correct (Compilable), Example) that demonstrates the problem. Note that the code should be as short as possible and not include components and methods irrelevant to the stated problem or inane IDE-generated comments.

db

[coderX]

Nvm guys,I made the program to work in such a way that it only refreshes when the data in the database changes.Thank you all for your time! :)

[Lionlev]

Nvm guys,I made the program to work in such a way that it only refreshes when the data in the database changes.Thank you all for your time! :)

Ok cool, glad to hear you made it work :D
Good luck with your creations

[joolske]

coderX, could you tell me exactly how you did this? the fact that it only refreshes when the data in the database change, is exactly what I need.