JTextArea中显示LineNumber

文章作者 100test 发表时间 2007:05:02 15:20:52
来源 100Test.Com百考试题网

//package tryLineNumber.

import java.awt.BorderLayout.
import java.awt.Dimension.
import java.awt.Graphics.
import java.awt.Point.

import javax.swing.JFrame.
import javax.swing.JTextArea.
import javax.swing.JPanel.
import javax.swing.JScrollPane.
//import javax.swing.JTextPane.
import javax.swing.text.BadLocationException.
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.

*
* @author Daniel Sj?blom

* Created on Mar 3, 2004

* Copyright (c) 2004

* @version 1.0

*/
public class LineNr extends JPanel
{
// for this simple experiment, we keep the pane scrollpane as members.
//JTextPane pane.
JTextArea 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
pane = new JTextArea()
{
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) 1.
int endline = doc.getDefaultRootElement().getElementIndex(end) 1.

int fontHeight = g.getFontMetrics(pane.getFont()).getHeight().
int fontDesc = g.getFontMetrics(pane.getFont()).getDescent().
int starting_y = -1.

try
{
starting_y = pane.modelToView(start).y -
scrollPane.getViewport().getViewPosition().y fontHeight - fontDesc.
}
catch (BadLocationException e1)
{
e1.printStackTrace().
}

for (int line = startline, y = starting_y. line <= endline. y = fontHeight, line )
{
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().
}

}