ActionListener for a specific text inside a JTextArea?

Solution 1:

Here try this small program, try to click at the start of student://, that will pop up a message Dialog

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class TextAreaExample extends JFrame
{
    private JTextArea tarea =  new JTextArea(10, 10);
    private JTextField tfield = new JTextField(10);

    private void createAndDisplayGUI()
    {
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        tarea.setText("Hello there\n");
        tarea.append("Hello student://");
        JScrollPane scroll = new JScrollPane(tarea);

        tfield.addActionListener(new ActionListener()
        {
            public void actionPerformed(ActionEvent ae)
            {
                tarea.append(tfield.getText() + "\n");
            }
        });

        tarea.addMouseListener(new MouseAdapter()
        {
            public void mouseClicked(MouseEvent me)
            {
                int x = me.getX();
                int y = me.getY();
                System.out.println("X : " + x);
                System.out.println("Y : " + y);
                int startOffset = tarea.viewToModel(new Point(x, y));
                System.out.println("Start Offset : " + startOffset);
                String text = tarea.getText();
                int searchLocation = text.indexOf("student://", startOffset);
                System.out.println("Search Location : " + searchLocation);
                if (searchLocation == startOffset)
                    JOptionPane.showMessageDialog(TextAreaExample.this, "BINGO you found me.");
            }
        });

        getContentPane().add(scroll, BorderLayout.CENTER);
        getContentPane().add(tfield, BorderLayout.PAGE_END);
        pack();
        setLocationByPlatform(true);
        setVisible(true);
    }

    public static void main(String... args)
    {
        SwingUtilities.invokeLater(new Runnable()
        {
            public void run()
            {
                new TextAreaExample().createAndDisplayGUI();
            }
        });
    }
}

Solution 2:

No, don't even consider this since ActionListeners are for JButtons or anything else derived from AbstractButton but not for JTextComponents (except for JTextFields). Perhaps you want a MouseListener.

Having said this, perhaps you'll be better off with two text components, a JTextArea to display all responses, including the user's, and right below this in a BorderLayout.SOUTH type of position, a JTextField to allow the user to enter text into the chat. Then give that JTextField an ActionListener (this is legal) so that "enter" will actuate the listener.

Edit 1
You state:

Well I have that jtextfield , the text in it is being sent to the server and server sends the message to all clients which appears in the JTextArea. But my problem is here: I want to popup a window when someone clicks on a student://id text .

Yeah, looking at your comments, my vote is for you to display the chats not in a JTextArea but rather in a JList, one with a SelectionListener. You can then respond easily to mouse click events, and will more easily get useful information from the "line" clicked on (if you fill the JList with smart objects). You will need to write a custom cell renderer that allows multiple lines of text to be displayed, probably one that shows a JTextArea, but the tutorial on JLists will get you started on this.

Solution 3:

Is hitting ENTER instead of mouse-click ok?

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;

public class StudentID extends JFrame implements ActionListener
{
    private static final String progname = "StudentID 0.1";

    private JTextField student;
    private JTextArea feedback;
    private JButton exit;

    public StudentID ()
    {
        super (progname);
        JPanel mainpanel = new JPanel ();
        mainpanel.setLayout (new BorderLayout ());
        this.getContentPane ().add (mainpanel);

        student = new JTextField ("student://");
        exit = new JButton ("exit");
        student.addActionListener (this);
        exit.addActionListener (this);
        feedback = new JTextArea ();
        mainpanel.add (student, BorderLayout.NORTH);
        mainpanel.add (feedback, BorderLayout.CENTER);
        mainpanel.add (exit, BorderLayout.SOUTH);

        setSize (400, 400);
        setLocation (100, 100);
        setDefaultCloseOperation (JFrame.EXIT_ON_CLOSE);
        setVisible (true);
    }

    public void actionPerformed (final ActionEvent e)
    {
        SwingWorker worker = new SwingWorker () 
        {
            protected String doInBackground () throws InterruptedException 
            {
                String cmd = e.getActionCommand ();
                if (cmd.equals ("exit"))
                {
                    System.exit (0);
                }
                else if (cmd.matches ("student://[0-9]+")) 
                {
                    feedback.setText ("student found: " + cmd.replaceAll ("student://([0-9]+)", "$1"));
                }
                else
                {
                    feedback.setText ("cmd: " + cmd);
                }
                return "done";
            }
            protected void done () 
            {
                feedback.setText (feedback.getText () + "\ndone");
            }
        };
        worker.execute ();
    }

    public static void main (final String args[])
    {
        Runnable runner = new Runnable () 
        {
            public void run () 
            {
                new StudentID ();
            }
        };
        EventQueue.invokeLater (runner);
    }
}