Fabrice said:
Hi !
I would like to know if it is possible to display the line number in a
JTextPane ? I design an editor and I'd like to offer the same feature
than a programer's notepad that show the number of EACH line at the
left side of the text.
It is fairly easy, but requires knowledge of swing idiosynchrasies. Here
is some code to get you started (probably munged by posting, try loading
it up in a beautifying editor):
package com.dsjoblom.junk;
import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Point;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextPane;
import javax.swing.text.Document;
/**
* A class illustrating running line number count on JTextPane. Nothing
is painted on the pane itself,
* but a separate JPanel handles painting the line numbers.<br>
*
* @author Daniel Sjöblom<br>
* Created on Mar 3, 2004<br>
* Copyright (c) 2004<br>
* @version 1.0<br>
*/
public class LineNr extends JPanel
{
// for this simple experiment, we keep the pane + scrollpane as members.
JTextPane pane;
JScrollPane scrollPane;
public LineNr()
{
super();
setMinimumSize(new Dimension(30, 30));
setPreferredSize(new Dimension(30, 30));
setMinimumSize(new Dimension(30, 30));
pane = new JTextPane() // we need to override paint so that the
linenumbers stay in sync
{
public void paint(Graphics g)
{
super.paint(g);
LineNr.this.repaint();
}
};
scrollPane = new JScrollPane(pane);
}
public void paint(Graphics g)
{
super.paint(g);
// We need to properly convert the points to match the viewport
// Read docs for viewport
int start =
pane.viewToModel(scrollPane.getViewport().getViewPosition()); //
starting pos in document
int end =
pane.viewToModel(
new Point(
scrollPane.getViewport().getViewPosition().x + pane.getWidth(),
scrollPane.getViewport().getViewPosition().y + pane.getHeight()));
// end pos in doc
// translate offsets to lines
Document doc = pane.getDocument();
int startline = doc.getDefaultRootElement().getElementIndex(start);
int endline = doc.getDefaultRootElement().getElementIndex(end);
int fontHeight = g.getFontMetrics(pane.getFont()).getHeight(); // font
height
for (int line = startline, y = 0; line <= endline; line++, y +=
fontHeight)
{
g.drawString(Integer.toString(line), 0, y);
}
}
// test main
public static void main(String[] args)
{
JFrame frame = new JFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().setLayout(new BorderLayout());
final LineNr nr = new LineNr();
frame.getContentPane().add(nr, BorderLayout.WEST);
frame.getContentPane().add(nr.scrollPane, BorderLayout.CENTER);
frame.pack();
frame.setSize(new Dimension(400, 400));
frame.show();
}
}
