或者，您可以使用以下类：
import javax.swing.*;
import javax.swing.border.Border;
import javax.swing.border.CompoundBorder;
import javax.swing.border.EmptyBorder;
import javax.swing.border.MatteBorder;
import javax.swing.event.CaretEvent;
import javax.swing.event.CaretListener;
import javax.swing.event.DocumentEvent;
import javax.swing.event.DocumentListener;
import javax.swing.text.*;
import java.awt.*;
import java.beans.PropertyChangeEvent;
import java.beans.PropertyChangeListener;
import java.util.HashMap;
/**
* 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.
* <p>
* 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.
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
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<>();
}
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(() ->
{
try
{
int endPos = component.getDocument().getLength();
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();
}
}
}
}
然后可以像这样添加行号：
TextLineNumber textLineNumber = new TextLineNumber(sourceCodeArea);
sourceCodeAreaScrollPane.setRowHeaderView(textLineNumber);