Testei um fonte muito bacana que alguém disponibilizou neste link.
Trata-se de uma classe que, quando utilizada como o rowHeaderView de um JScrollPane, renderiza o número da linha de qualquer JTextComponent.
Exemplo de utilização:
import java.awt.BorderLayout;
import javax.swing.JFrame;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
public class Exemplo {
public static void main(String[] args) {
try {
JTextArea areaDeTexto = new JTextArea();
JScrollPane painelComBarraDeRolagem = new JScrollPane(areaDeTexto);
TextLineNumber contadorLinhas = new TextLineNumber(areaDeTexto);
painelComBarraDeRolagem.setRowHeaderView(contadorLinhas);
JFrame janela = new JFrame("Exemplo");
janela.add(BorderLayout.CENTER, painelComBarraDeRolagem);
janela.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
janela.setSize(640, 480);
janela.setLocationRelativeTo(null);
janela.setVisible(true);
} catch (Exception e) {
e.printStackTrace();
}
}
}
E aqui está a classe que faz toda a mágica acontecer:
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Font;
import java.awt.FontMetrics;
import java.awt.Graphics;
import java.awt.Insets;
import java.awt.Point;
import java.awt.Rectangle;
import java.beans.PropertyChangeEvent;
import java.beans.PropertyChangeListener;
import java.util.HashMap;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
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.AttributeSet;
import javax.swing.text.BadLocationException;
import javax.swing.text.Element;
import javax.swing.text.JTextComponent;
import javax.swing.text.StyleConstants;
import javax.swing.text.Utilities;
public class TextLineNumber extends JPanel implements CaretListener, DocumentListener, PropertyChangeListener {
private static final long serialVersionUID = 1;
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;
private JTextComponent component;
private boolean updateFont;
private int borderGap;
private Color currentLineForeground;
private float digitAlignment;
private int minimumDisplayDigits;
private int lastDigits;
private int lastHeight;
private int lastLine;
private HashMap<String, FontMetrics> fonts;
public TextLineNumber(JTextComponent component) {
this(component, 3);
}
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);
}
public boolean getUpdateFont() {
return updateFont;
}
public void setUpdateFont(boolean updateFont) {
this.updateFont = updateFont;
}
public int getBorderGap() {
return borderGap;
}
public void setBorderGap(int borderGap) {
this.borderGap = borderGap;
Border inner = new EmptyBorder(0, borderGap, 0, borderGap);
setBorder(new CompoundBorder(OUTER, inner));
lastDigits = 0;
setPreferredWidth();
}
public Color getCurrentLineForeground() {
return currentLineForeground == null ? getForeground() : currentLineForeground;
}
public void setCurrentLineForeground(Color currentLineForeground) {
this.currentLineForeground = currentLineForeground;
}
public float getDigitAlignment() {
return digitAlignment;
}
public void setDigitAlignment(float digitAlignment) {
this.digitAlignment = digitAlignment > 1.0f ? 1.0f : digitAlignment < 0.0f ? -1.0f : digitAlignment;
}
public int getMinimumDisplayDigits() {
return minimumDisplayDigits;
}
public void setMinimumDisplayDigits(int minimumDisplayDigits) {
this.minimumDisplayDigits = minimumDisplayDigits;
setPreferredWidth();
}
private void setPreferredWidth() {
Element root = component.getDocument().getDefaultRootElement();
int lines = root.getElementCount();
int digits = Math.max(String.valueOf(lines).length(), minimumDisplayDigits);
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);
}
}
@Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
FontMetrics fontMetrics = component.getFontMetrics(component.getFont());
Insets insets = getInsets();
int availableWidth = getSize().width - insets.left - insets.right;
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());
}
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);
rowStartOffset = Utilities.getRowEnd(component, rowStartOffset) + 1;
} catch (Exception e) {
break;
}
}
}
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;
}
}
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 "";
}
}
private int getOffsetX(int availableWidth, int stringWidth) {
return (int) ((availableWidth - stringWidth) * digitAlignment);
}
private int getOffsetY(int rowStartOffset, FontMetrics fontMetrics) throws BadLocationException {
Rectangle r = component.modelToView(rowStartOffset);
int lineHeight = fontMetrics.getHeight();
int y = r.y + r.height;
int descent = 0;
if (r.height == lineHeight) {
descent = fontMetrics.getDescent();
} else {
if (fonts == null)
fonts = new HashMap<String, FontMetrics>();
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;
}
@Override
public void caretUpdate(CaretEvent e) {
int caretPosition = component.getCaretPosition();
Element root = component.getDocument().getDefaultRootElement();
int currentLine = root.getElementIndex(caretPosition);
if (lastLine != currentLine) {
repaint();
lastLine = currentLine;
}
}
@Override
public void changedUpdate(DocumentEvent e) {
documentChanged();
}
@Override
public void insertUpdate(DocumentEvent e) {
documentChanged();
}
@Override
public void removeUpdate(DocumentEvent e) {
documentChanged();
}
private void documentChanged() {
SwingUtilities.invokeLater(new Runnable() {
@Override
public void run() {
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) {}
}
});
}
@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();
}
}
}
}
Por hoje é só pessoal!