JTextArea中显示LineNumber

月下独舞

//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.<br> * * @author Daniel Sj?blom<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; 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(); } }