Thread: How To: Add line numbers to your JTextArea

very good one...thanks a lot

OK, so this seemed to be a popular code snippet, and with a request of highlighting i have decided to actually do it. Sorry it took so longer but here it is.

import java.awt.Color;
import java.awt.event.FocusEvent;
import java.awt.event.FocusListener;
import java.awt.event.MouseEvent;
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.event.MouseInputListener;
import javax.swing.text.BadLocationException;
import javax.swing.text.Element;
import javax.swing.text.Highlighter;
 
 
public class MainWindow extends JFrame implements MouseInputListener, DocumentListener, FocusListener{
	private JTextArea jta;
	private JTextArea lines;
	private Highlighter highlighter;
 
	public MainWindow(){
		super("Line Numbering & Highlighter Example");
	}
	public void createAndShowGUI(){
		/* Set up frame */
		JFrame frame = new MainWindow();
		frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
 
		/* Set up JtextArea */
		jta = new JTextArea();
		jta.getDocument().addDocumentListener(this);
 
		/* Set up Highlighter */
		highlighter = jta.getHighlighter();
 
		/* Set up line numbers */
		lines = new JTextArea("1");
		lines.setBackground(Color.LIGHT_GRAY);
		lines.setEditable(false);
		lines.addMouseListener(this);
		lines.addFocusListener(this);
 
		/* Set up scroll pane */
		JScrollPane jsp = new JScrollPane();
		jsp.getViewport().add(jta);
		jsp.setRowHeaderView(lines);
		jsp.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);
 
		jta.setText("Hello world how are you today!");
 
		/* pack and show frame */
		frame.add(jsp);
		frame.pack();
		frame.setSize(500,500);
		frame.setVisible(true);
	}
 
	/* Document Listener Events */
	public void changedUpdate(DocumentEvent de) {
		lines.setText(getText());
	}
	public void insertUpdate(DocumentEvent de) {
		lines.setText(getText());
	}
	public void removeUpdate(DocumentEvent de) {
		lines.setText(getText());
	}
	public String getText(){
		int caretPosition = jta.getDocument().getLength();
		Element root = jta.getDocument().getDefaultRootElement();
		String text = "1\n";
		for(int i = 2; i < root.getElementIndex( caretPosition ) + 2; i++)
			text += i + "\n";
		return text;
	}
 
	/* Mouse Listener Events */
	public void mouseClicked(MouseEvent me) {
		if(me.getClickCount() == 2){
			try {
				int caretPos = lines.getCaretPosition();
				int lineOffset = lines.getLineOfOffset(caretPos);
				if(lines.getText().charAt(caretPos-1) == '\n')
					lineOffset--;
				highlighter.addHighlight(jta.getLineStartOffset(lineOffset),
										 jta.getLineEndOffset(lineOffset), 
										 new MyHighlighter(Color.cyan));
			} catch (BadLocationException e) {
				e.printStackTrace();
			}
		}
	}
	public void mouseEntered(MouseEvent me) {}
	public void mouseExited(MouseEvent me) {}
	public void mousePressed(MouseEvent me) {}
	public void mouseReleased(MouseEvent me) {}
	public void mouseDragged(MouseEvent me) {}
	public void mouseMoved(MouseEvent me) {}
 
	/* Focus Listener Events for line numbers*/
	public void focusGained(FocusEvent fe) {}
	public void focusLost(FocusEvent fe) {
		highlighter.removeAllHighlights();
	}
	public static void main(String[] args){
		javax.swing.SwingUtilities.invokeLater(new Runnable() {
                                                   public void run() {
                                                              new MainWindow().createAndShowGUI();
                                                   }
                                           });
	}
}
[/code]
[code]
import java.awt.Color;
import javax.swing.text.DefaultHighlighter;
 
public class MyHighlighter extends DefaultHighlighter.DefaultHighlightPainter {
	public MyHighlighter(Color c) {
		super(c);
	}
}

Enjoy,

Chris

That one is good, though it doesn't work well with different font sizes and was ending too short of the actual end line. This code I found online works better.

 
 
import java.awt.*;
import java.awt.event.*;
import java.beans.*;
import java.util.HashMap;
import javax.swing.*;
import javax.swing.border.*;
import javax.swing.event.*;
import javax.swing.text.*;
 
/**
 *  This class will display line numbers for a related text component. The text
 *  component must use the same line height for each line. TextLineNumber
 *  supports wrapped lines and will highlight the line number of the current
 *  line in the text component.
 *
 *  This class was designed to be used as a component added to the row header
 *  of a JScrollPane.
 */
public class TextLineNumber extends JPanel
	implements CaretListener, DocumentListener, PropertyChangeListener
{
   public final static float LEFT = 0.0f;
   public final static float CENTER = 0.5f;
   public final static float RIGHT = 1.0f;
 
   private final static Border OUTER = new MatteBorder(0, 0, 0, 2, Color.GRAY);
 
   private final static int HEIGHT = Integer.MAX_VALUE - 1000000;
 
	//  Text component this TextTextLineNumber component is in sync with
 
   private JTextComponent component;
 
	//  Properties that can be changed
 
   private boolean updateFont;
   private int borderGap;
   private Color currentLineForeground;
   private float digitAlignment;
   private int minimumDisplayDigits;
 
	//  Keep history information to reduce the number of times the component
	//  needs to be repainted
 
   private int lastDigits;
   private int lastHeight;
   private int lastLine;
 
   private HashMap<String, FontMetrics> fonts;
 
	/**
	 *	Create a line number component for a text component. This minimum
	 *  display width will be based on 3 digits.
	 *
	 *  @param component  the related text component
	 */
   public TextLineNumber(JTextComponent component)
   {
      this(component, 3);
   }
 
	/**
	 *	Create a line number component for a text component.
	 *
	 *  @param component  the related text component
	 *  @param minimumDisplayDigits  the number of digits used to calculate
	 *                               the minimum width of the component
	 */
   public TextLineNumber(JTextComponent component, int minimumDisplayDigits)
   {
      this.component = component;
 
      setFont( component.getFont() );
 
      setBorderGap( 5 );
      setCurrentLineForeground( Color.RED );
      setDigitAlignment( RIGHT );
      setMinimumDisplayDigits( minimumDisplayDigits );
 
      component.getDocument().addDocumentListener(this);
      component.addCaretListener( this );
      component.addPropertyChangeListener("font", this);
   }
 
	/**
	 *  Gets the update font property
	 *
	 *  @return the update font property
	 */
   public boolean getUpdateFont()
   {
      return updateFont;
   }
 
	/**
	 *  Set the update font property. Indicates whether this Font should be
	 *  updated automatically when the Font of the related text component
	 *  is changed.
	 *
	 *  @param updateFont  when true update the Font and repaint the line
	 *                     numbers, otherwise just repaint the line numbers.
	 */
   public void setUpdateFont(boolean updateFont)
   {
      this.updateFont = updateFont;
   }
 
	/**
	 *  Gets the border gap
	 *
	 *  @return the border gap in pixels
	 */
   public int getBorderGap()
   {
      return borderGap;
   }
 
	/**
	 *  The border gap is used in calculating the left and right insets of the
	 *  border. Default value is 5.
	 *
	 *  @param borderGap  the gap in pixels
	 */
   public void setBorderGap(int borderGap)
   {
      this.borderGap = borderGap;
      Border inner = new EmptyBorder(0, borderGap, 0, borderGap);
      setBorder( new CompoundBorder(OUTER, inner) );
      lastDigits = 0;
      setPreferredWidth();
   }
 
	/**
	 *  Gets the current line rendering Color
	 *
	 *  @return the Color used to render the current line number
	 */
   public Color getCurrentLineForeground()
   {
      return currentLineForeground == null ? getForeground() : currentLineForeground;
   }
 
	/**
	 *  The Color used to render the current line digits. Default is Coolor.RED.
	 *
	 *  @param currentLineForeground  the Color used to render the current line
	 */
   public void setCurrentLineForeground(Color currentLineForeground)
   {
      this.currentLineForeground = currentLineForeground;
   }
 
	/**
	 *  Gets the digit alignment
	 *
	 *  @return the alignment of the painted digits
	 */
   public float getDigitAlignment()
   {
      return digitAlignment;
   }
 
	/**
	 *  Specify the horizontal alignment of the digits within the component.
	 *  Common values would be:
	 *  <ul>
	 *  <li>TextLineNumber.LEFT
	 *  <li>TextLineNumber.CENTER
	 *  <li>TextLineNumber.RIGHT (default)
	 *	</ul>
	 *  @param currentLineForeground  the Color used to render the current line
	 */
   public void setDigitAlignment(float digitAlignment)
   {
      this.digitAlignment =
         digitAlignment > 1.0f ? 1.0f : digitAlignment < 0.0f ? -1.0f : digitAlignment;
   }
 
	/**
	 *  Gets the minimum display digits
	 *
	 *  @return the minimum display digits
	 */
   public int getMinimumDisplayDigits()
   {
      return minimumDisplayDigits;
   }
 
	/**
	 *  Specify the mimimum number of digits used to calculate the preferred
	 *  width of the component. Default is 3.
	 *
	 *  @param minimumDisplayDigits  the number digits used in the preferred
	 *                               width calculation
	 */
   public void setMinimumDisplayDigits(int minimumDisplayDigits)
   {
      this.minimumDisplayDigits = minimumDisplayDigits;
      setPreferredWidth();
   }
 
	/**
	 *  Calculate the width needed to display the maximum line number
	 */
   private void setPreferredWidth()
   {
      Element root = component.getDocument().getDefaultRootElement();
      int lines = root.getElementCount();
      int digits = Math.max(String.valueOf(lines).length(), minimumDisplayDigits);
 
   	//  Update sizes when number of digits in the line number changes
 
      if (lastDigits != digits)
      {
         lastDigits = digits;
         FontMetrics fontMetrics = getFontMetrics( getFont() );
         int width = fontMetrics.charWidth( '0' ) * digits;
         Insets insets = getInsets();
         int preferredWidth = insets.left + insets.right + width;
 
         Dimension d = getPreferredSize();
         d.setSize(preferredWidth, HEIGHT);
         setPreferredSize( d );
         setSize( d );
      }
   }
 
	/**
	 *  Draw the line numbers
	 */
   @Override
   public void paintComponent(Graphics g)
   {
      super.paintComponent(g);
 
   	//	Determine the width of the space available to draw the line number
 
      FontMetrics fontMetrics = component.getFontMetrics( component.getFont() );
      Insets insets = getInsets();
      int availableWidth = getSize().width - insets.left - insets.right;
 
   	//  Determine the rows to draw within the clipped bounds.
 
      java.awt.Rectangle clip = g.getClipBounds();
      int rowStartOffset = component.viewToModel( new Point(0, clip.y) );
      int endOffset = component.viewToModel( new Point(0, clip.y + clip.height) );
 
      while (rowStartOffset <= endOffset)
      {
         try
         {
            if (isCurrentLine(rowStartOffset))
               g.setColor( getCurrentLineForeground() );
            else
               g.setColor( getForeground() );
 
         	//  Get the line number as a string and then determine the
         	//  "X" and "Y" offsets for drawing the string.
 
            String lineNumber = getTextLineNumber(rowStartOffset);
            int stringWidth = fontMetrics.stringWidth( lineNumber );
            int x = getOffsetX(availableWidth, stringWidth) + insets.left;
            int y = getOffsetY(rowStartOffset, fontMetrics);
            g.drawString(lineNumber, x, y);
 
         	//  Move to the next row
 
            rowStartOffset = Utilities.getRowEnd(component, rowStartOffset) + 1;
         }
         catch(Exception e) {
            break;}
      }
   }
 
	/*
	 *  We need to know if the caret is currently positioned on the line we
	 *  are about to paint so the line number can be highlighted.
	 */
   private boolean isCurrentLine(int rowStartOffset)
   {
      int caretPosition = component.getCaretPosition();
      Element root = component.getDocument().getDefaultRootElement();
 
      if (root.getElementIndex( rowStartOffset ) == root.getElementIndex(caretPosition))
         return true;
      else
         return false;
   }
 
	/*
	 *	Get the line number to be drawn. The empty string will be returned
	 *  when a line of text has wrapped.
	 */
   protected String getTextLineNumber(int rowStartOffset)
   {
      Element root = component.getDocument().getDefaultRootElement();
      int index = root.getElementIndex( rowStartOffset );
      Element line = root.getElement( index );
 
      if (line.getStartOffset() == rowStartOffset)
         return String.valueOf(index + 1);
      else
         return "";
   }
 
	/*
	 *  Determine the X offset to properly align the line number when drawn
	 */
   private int getOffsetX(int availableWidth, int stringWidth)
   {
      return (int)((availableWidth - stringWidth) * digitAlignment);
   }
 
	/*
	 *  Determine the Y offset for the current row
	 */
   private int getOffsetY(int rowStartOffset, FontMetrics fontMetrics)
   	throws BadLocationException
   {
   	//  Get the bounding rectangle of the row
 
      java.awt.Rectangle r = component.modelToView( rowStartOffset );
      int lineHeight = fontMetrics.getHeight();
      int y = r.y + r.height;
      int descent = 0;
 
   	//  The text needs to be positioned above the bottom of the bounding
   	//  rectangle based on the descent of the font(s) contained on the row.
 
      if (r.height == lineHeight)  // default font is being used
      {
         descent = fontMetrics.getDescent();
      }
      else  // We need to check all the attributes for font changes
      {
         if (fonts == null)
            fonts = new HashMap<String, FontMetrics>();
 
         Element root = component.getDocument().getDefaultRootElement();
         int index = root.getElementIndex( rowStartOffset );
         Element line = root.getElement( index );
 
         for (int i = 0; i < line.getElementCount(); i++)
         {
            Element child = line.getElement(i);
            AttributeSet as = child.getAttributes();
            String fontFamily = (String)as.getAttribute(StyleConstants.FontFamily);
            Integer fontSize = (Integer)as.getAttribute(StyleConstants.FontSize);
            String key = fontFamily + fontSize;
 
            FontMetrics fm = fonts.get( key );
 
            if (fm == null)
            {
               Font font = new Font(fontFamily, Font.PLAIN, fontSize);
               fm = component.getFontMetrics( font );
               fonts.put(key, fm);
            }
 
            descent = Math.max(descent, fm.getDescent());
         }
      }
 
      return y - descent;
   }
 
//
//  Implement CaretListener interface
//
   @Override
   public void caretUpdate(CaretEvent e)
   {
   	//  Get the line the caret is positioned on
 
      int caretPosition = component.getCaretPosition();
      Element root = component.getDocument().getDefaultRootElement();
      int currentLine = root.getElementIndex( caretPosition );
 
   	//  Need to repaint so the correct line number can be highlighted
 
      if (lastLine != currentLine)
      {
         repaint();
         lastLine = currentLine;
      }
   }
 
//
//  Implement DocumentListener interface
//
   @Override
   public void changedUpdate(DocumentEvent e)
   {
      documentChanged();
   }
 
   @Override
   public void insertUpdate(DocumentEvent e)
   {
      documentChanged();
   }
 
   @Override
   public void removeUpdate(DocumentEvent e)
   {
      documentChanged();
   }
 
	/*
	 *  A document change may affect the number of displayed lines of text.
	 *  Therefore the lines numbers will also change.
	 */
   private void documentChanged()
   {
   	//  View of the component has not been updated at the time
   	//  the DocumentEvent is fired
 
      SwingUtilities.invokeLater(
            new Runnable()
            {
               @Override
               public void run()
               {
                  try
                  {
                     int endPos = component.getDocument().getLength();
                     java.awt.Rectangle rect = component.modelToView(endPos);
 
                     if (rect != null && rect.y != lastHeight)
                     {
                        setPreferredWidth();
                        repaint();
                        lastHeight = rect.y;
                     }
                  }
                  catch (BadLocationException ex) { /* nothing to do */ }
               }
            });
   }
 
//
//  Implement PropertyChangeListener interface
//
   @Override
   public void propertyChange(PropertyChangeEvent evt)
   {
      if (evt.getNewValue() instanceof Font)
      {
         if (updateFont)
         {
            Font newFont = (Font) evt.getNewValue();
            setFont(newFont);
            lastDigits = 0;
            setPreferredWidth();
         }
         else
         {
            repaint();
         }
      }
   }
 
   public static void main(String[] args)
   {
 
 
      javax.swing.JFrame jf = new javax.swing.JFrame();
 
      jf.setVisible(true);
 
      JTextArea ta = new JTextArea(25, 25);
 
      javax.swing.JScrollPane sp = new javax.swing.JScrollPane(ta, JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED, JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED);
 
 
      TextLineNumber tln = new TextLineNumber(ta);
      sp.setRowHeaderView( tln );
      jf.setContentPane(sp);
 
 
 
   }
}