Thread: How To: Add line numbers to your JTextArea

Thanks !!!

This very useful code. Also, that line highlighting sounds pretty interesting... If you have enough time, can you implement it, please?

Thanks you very much

Originally Posted by Freaky Chris

Well, I know a few people have wanted to do things like this before. So here is my code approach to it, enjoy. There are other methods I'm sure, but I think this is the easiest.

It makes use of the JScrollPane Row Header

import java.awt.Color;
 
import javax.swing.JFrame;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.event.DocumentEvent;
import javax.swing.event.DocumentListener;
import javax.swing.text.Element;
 
 
public class LineNumbering extends JFrame{
	private static JTextArea jta;
	private static JTextArea lines;
 
	public LineNumbering(){
		super("Line Numbering Example");
	}
 
	public static void createAndShowGUI(){
		JFrame frame = new LineNumbering();
		frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
 
		JScrollPane jsp = new JScrollPane();
		jta = new JTextArea();
		lines = new JTextArea("1");
 
		lines.setBackground(Color.LIGHT_GRAY);
		lines.setEditable(false);
 
		jta.getDocument().addDocumentListener(new DocumentListener(){
			public String getText(){
				int caretPosition = jta.getDocument().getLength();
				Element root = jta.getDocument().getDefaultRootElement();
				String text = "1" + System.getProperty("line.separator");
				for(int i = 2; i < root.getElementIndex( caretPosition ) + 2; i++){
					text += i + System.getProperty("line.separator");
				}
				return text;
			}
			@Override
			public void changedUpdate(DocumentEvent de) {
				lines.setText(getText());
			}
 
			@Override
			public void insertUpdate(DocumentEvent de) {
				lines.setText(getText());
			}
 
			@Override
			public void removeUpdate(DocumentEvent de) {
				lines.setText(getText());
			}
 
		});
 
		jsp.getViewport().add(jta);
		jsp.setRowHeaderView(lines);
		jsp.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);
 
		frame.add(jsp);
		frame.pack();
		frame.setSize(500,500);
		frame.setVisible(true);
	}
 
	public static void main(String[] args){
		javax.swing.SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                createAndShowGUI();
            }
        });
	}
}

Chris

Thnks dis helped me a lot but could u plz provide some explanation abt dis code would of greta help.....

Good code.

Originally Posted by Freaky Chris

Well, I know a few people have wanted to do things like this before. So here is my code approach to it, enjoy. There are other methods I'm sure, but I think this is the easiest.

It makes use of the JScrollPane Row Header

import java.awt.Color;
 
import javax.swing.JFrame;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.event.DocumentEvent;
import javax.swing.event.DocumentListener;
import javax.swing.text.Element;
 
 
public class LineNumbering extends JFrame{
	private static JTextArea jta;
	private static JTextArea lines;
 
	public LineNumbering(){
		super("Line Numbering Example");
	}
 
	public static void createAndShowGUI(){
		JFrame frame = new LineNumbering();
		frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
 
		JScrollPane jsp = new JScrollPane();
		jta = new JTextArea();
		lines = new JTextArea("1");
 
		lines.setBackground(Color.LIGHT_GRAY);
		lines.setEditable(false);
 
		jta.getDocument().addDocumentListener(new DocumentListener(){
			public String getText(){
				int caretPosition = jta.getDocument().getLength();
				Element root = jta.getDocument().getDefaultRootElement();
				String text = "1" + System.getProperty("line.separator");
				for(int i = 2; i < root.getElementIndex( caretPosition ) + 2; i++){
					text += i + System.getProperty("line.separator");
				}
				return text;
			}
			@Override
			public void changedUpdate(DocumentEvent de) {
				lines.setText(getText());
			}
 
			@Override
			public void insertUpdate(DocumentEvent de) {
				lines.setText(getText());
			}
 
			@Override
			public void removeUpdate(DocumentEvent de) {
				lines.setText(getText());
			}
 
		});
 
		jsp.getViewport().add(jta);
		jsp.setRowHeaderView(lines);
		jsp.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);
 
		frame.add(jsp);
		frame.pack();
		frame.setSize(500,500);
		frame.setVisible(true);
	}
 
	public static void main(String[] args){
		javax.swing.SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                createAndShowGUI();
            }
        });
	}
}

Chris

Hello! I have a doubt.
Everytime I modify the text in the JTextArea, the "number area" updates and scrolls down to the end. I mean, if I write a character at line 67 out of 100, the "line number area" shows me 95 96 97 98 99 100... just the end and it doesn't stays at that line number (67 in this case).

How can I fix that? I'm kind of stuck there.

I hope you can help me.
Thanks.

hi all,

i am new to this forum, so at first i just want so say hello to all :-)

i have a little project implementing some own grammar language
for some german linguists and want to have a nice little IDE
to edit those grammars ...
so i startet to create some basic IDE features with swing
an netbeans.
i used the code here and found, which seems very helpful for me,
but i also noticed some problems ...

1. display of linenumbers
in some circumstances the scrolling of the editor component and the
line header in scoll bar are not synchronized.
which means scrolling posion is not the same and the displayed lineno
does not represent the actual one ...
i currently not know how to sync theese components ... :-(

2. jtextpane and linewrap
for syntaxhighlighing functions i need jtextpane insted of
jtextarea.
out of the box you can't easly turnoff linewrapping in jtextpane.
if you use a little trick and enclose the jtextpane in a pane which
layout is set to 'border' you can simulate no line wrap.
the problem is, if you type out of the viewport you cant see the edit-
cursor, which is out of the viewport ...
maybe this also have to be synced somehow with scrolling ...

maybe anybody has a great idea or some useful experience on this :-)

thank you in andvance

regards
patrick