java显示行号

java显示行号 package pack03; //JTextArea ÖÐÏÔÊ?ÐкŠ//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.text.BadLocationException; import javax.swing.text.Document; public class LineNr extends JPanel { /** * */ private static final long serialVersionUID = 5725882114351953053L; JTextArea pane; JScrollPane scrollPane; public LineNr() { super(); setMinimumSize(new Dimension(30, 30)); setPreferredSize(new Dimension(30, 30)); setMinimumSize(new Dimension(30, 30)); pane = new JTextArea() { /** * */ private static final long serialVersionUID = 1L; public void paint(Graphics g) { super.paint(g); LineNr.this.repaint(); } }; scrollPane = new JScrollPane(pane); } public void paint(Graphics g) { super.paint(g); int start =pane.viewToModel(scrollPane.getViewport().getViewPosition()); int end = pane.viewToModel( new Point( scrollPane.getViewport().getViewPosition().x + pane.getWidth(), scrollPane.getViewport().getViewPosition().y + pane.getHeight())); 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.setVisible(true); } }