How can we display the line numbers inside a JTextArea in Java?
例
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 | import java.awt.*; import javax.swing.*; import javax.swing.event.*; import javax.swing.text.Element; public class LineNumberTextAreaTest extends JFrame { private static JTextArea textArea; private static JTextArea lines; private JScrollPane jsp; public LineNumberTextAreaTest() { setTitle("LineNumberTextArea Test"); jsp = new JScrollPane(); textArea = new JTextArea(); lines = new JTextArea("1"); lines.setBackground(Color.LIGHT_GRAY); lines.setEditable(false); // Code to implement line numbers inside the JTextArea textArea.getDocument().addDocumentListener(new DocumentListener() { public String getText() { int caretPosition = textArea.getDocument().getLength(); Element root = textArea.getDocument().getDefaultRootElement(); String text ="1" + System.getProperty("line.separator"); for(int i = 2; i < root.getElementIndex(caretPosition) + 2; i++) { text += i + System.getProperty("line.separator"); } return text; } @Override public void changedUpdate(DocumentEvent de) { lines.setText(getText()); } @Override public void insertUpdate(DocumentEvent de) { lines.setText(getText()); } @Override public void removeUpdate(DocumentEvent de) { lines.setText(getText()); } }); jsp.getViewport().add(textArea); jsp.setRowHeaderView(lines); add(jsp); setSize(400, 275); setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); setLocationRelativeTo(null); setVisible(true); } public static void main(String[] args) { new LineNumberTextAreaTest(); } } |
输出量
