如何计算 JTextArea 中的行数，包括换行？

Question

我想计算 JTextArea 的行号，包括换行的文本。我从Here Thread得到了很好的示例代码

但我尝试使用动态 JTextArea 进行修改。但是行号的计算出错了。

这是我修改的代码：

package fandi.demo;

import java.awt.font.FontRenderContext;
import java.awt.font.LineBreakMeasurer;
import java.text.AttributedCharacterIterator;
import java.text.AttributedString;
import javax.swing.JTextArea;
import javax.swing.event.DocumentEvent;
import javax.swing.event.DocumentListener;

public class JTextAreaCountModified extends javax.swing.JFrame {

    public JTextAreaCountModified() {
        initComponents();
        setLocationRelativeTo(null);

        txtResult.getDocument().addDocumentListener(new DocumentListener() {

            @Override
            public void insertUpdate(DocumentEvent e) {
                if(txtResult.getText().length() > 0) {
                    lblCountLine.setText(String.valueOf(countLines(txtResult)));
                } else {
                    lblCountLine.setText("0");
                }
            }

            @Override
            public void removeUpdate(DocumentEvent e) {
                if(txtResult.getText().length() > 0) {
                    lblCountLine.setText(String.valueOf(countLines(txtResult)));
                }else {
                    lblCountLine.setText("0");
                }
            }

            @Override
            public void changedUpdate(DocumentEvent e) {
                if(txtResult.getText().length() > 0) {
                    lblCountLine.setText(String.valueOf(countLines(txtResult)));
                }else {
                    lblCountLine.setText("0");
                }
            }
        });
    }

    // COUNTING LINE GOES HERE...
    public static int countLines(JTextArea textArea) {
        AttributedString text = new AttributedString(textArea.getText());
        FontRenderContext frc = textArea.getFontMetrics(textArea.getFont()).getFontRenderContext();
        AttributedCharacterIterator charIt = text.getIterator();
        LineBreakMeasurer lineMeasurer = new LineBreakMeasurer(charIt, frc);
        float formatWidth = (float) textArea.getSize().width;
        lineMeasurer.setPosition(charIt.getBeginIndex());

        int noLines = 0;
        while (lineMeasurer.getPosition() < charIt.getEndIndex()) {
            lineMeasurer.nextLayout(formatWidth);
            noLines++;
        }

        int lineEnter = textArea.getLineCount();
        int countLine = noLines + lineEnter;

        return countLine-1;
    } 
    // END OF COUNTING METHOD

    /**
     * This method is called from within the constructor to initialize the form.
     * WARNING: Do NOT modify this code. The content of this method is always
     * regenerated by the Form Editor.
     */
    @SuppressWarnings("unchecked")
    // <editor-fold defaultstate="collapsed" desc="Generated Code">//GEN-BEGIN:initComponents
    private void initComponents() {

        jLabel1 = new javax.swing.JLabel();
        jLabel2 = new javax.swing.JLabel();
        jScrollPane1 = new javax.swing.JScrollPane();
        txtResult = new javax.swing.JTextArea();
        jLabel3 = new javax.swing.JLabel();
        lblCountLine = new javax.swing.JLabel();

        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
        setTitle("JTextArea Line Counting include Wrap");
        setResizable(false);

        jLabel1.setText("Enter paragraph");

        jLabel2.setFont(new java.awt.Font("Tahoma", 1, 11)); // NOI18N
        jLabel2.setForeground(new java.awt.Color(255, 0, 0));
        jLabel2.setText("20 line limit.");

        txtResult.setColumns(20);
        txtResult.setLineWrap(true);
        txtResult.setRows(5);
        txtResult.setWrapStyleWord(true);
        jScrollPane1.setViewportView(txtResult);

        jLabel3.setFont(new java.awt.Font("Tahoma", 1, 11)); // NOI18N
        jLabel3.setText("Information : ");

        lblCountLine.setText("...");

        javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addContainerGap()
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                    .addGroup(layout.createSequentialGroup()
                        .addComponent(jLabel3)
                        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                        .addComponent(lblCountLine)
                        .addGap(0, 0, Short.MAX_VALUE))
                    .addGroup(layout.createSequentialGroup()
                        .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                            .addComponent(jScrollPane1, javax.swing.GroupLayout.DEFAULT_SIZE, 458, Short.MAX_VALUE)
                            .addGroup(layout.createSequentialGroup()
                                .addComponent(jLabel1)
                                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                                .addComponent(jLabel2)
                                .addGap(0, 0, Short.MAX_VALUE)))
                        .addContainerGap())))
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addContainerGap()
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(jLabel1)
                    .addComponent(jLabel2))
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
                .addComponent(jScrollPane1, javax.swing.GroupLayout.PREFERRED_SIZE, 290, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addGap(18, 18, 18)
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(jLabel3)
                    .addComponent(lblCountLine))
                .addContainerGap(13, Short.MAX_VALUE))
        );

        pack();
    }// </editor-fold>//GEN-END:initComponents

    /**
     * @param args the command line arguments
     */
    public static void main(String args[]) {
        /* Set the Nimbus look and feel */
        //<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
        /* If Nimbus (introduced in Java SE 6) is not available, stay with the default look and feel.
         * For details see http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html 
         */
        try {
            for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
                if ("Nimbus".equals(info.getName())) {
                    javax.swing.UIManager.setLookAndFeel(info.getClassName());
                    break;
                }
            }
        } catch (ClassNotFoundException ex) {
            java.util.logging.Logger.getLogger(JTextAreaCountModified.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (InstantiationException ex) {
            java.util.logging.Logger.getLogger(JTextAreaCountModified.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (IllegalAccessException ex) {
            java.util.logging.Logger.getLogger(JTextAreaCountModified.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (javax.swing.UnsupportedLookAndFeelException ex) {
            java.util.logging.Logger.getLogger(JTextAreaCountModified.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        }
        //</editor-fold>

        /* Create and display the form */
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                new JTextAreaCountModified().setVisible(true);
            }
        });
    }
    // Variables declaration - do not modify//GEN-BEGIN:variables
    private javax.swing.JLabel jLabel1;
    private javax.swing.JLabel jLabel2;
    private javax.swing.JLabel jLabel3;
    private javax.swing.JScrollPane jScrollPane1;
    private javax.swing.JLabel lblCountLine;
    private javax.swing.JTextArea txtResult;
    // End of variables declaration//GEN-END:variables
}

请帮忙，谢谢:)

Answer 1

参见Text Utilities 中的getWrappedLines() 方法。

Answer 2

• 还有另一种，两种不同的方式，但我在行内使用循环，

.

import java.awt.BorderLayout;
import java.awt.Font;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.SwingUtilities;
import javax.swing.text.BadLocationException;
import javax.swing.text.Element;

public class ResizeJTextArea {

    private JFrame frame = new JFrame();
    private JScrollPane scrollPane = new JScrollPane();
    private JTextArea textArea = new JTextArea(15, 15);
    private JButton button = new JButton("change");
    private Font newFont = new Font("Courier", Font.PLAIN, 10);

    public ResizeJTextArea() {
        textArea.setText("This is just a line of text, "
                + "This is just a line of text, This is just a line of text, "
                + "This is just a line of text,\nThis is just a line of text,"
                + "This is just a line of text, This is just a line of text,"
                + "\nThis is just a line of text,This is just a line of text, "
                + "This is just a line of text,\nThis is just a line of text,"
                + "This is just a line of text, This is just a line of text,"
                + "\nThis is just a line of text, This is just a line of text,"
                + "\nThis is just a line of text,");
        textArea.setLineWrap(true);
        textArea.setWrapStyleWord(true);
        textArea.setFont(newFont);
        button.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                textArea.setFont(textArea.getFont().deriveFont(20f));
                frame.pack();
            }
        });
        scrollPane.setViewportView(textArea);
        frame.add(scrollPane);
        frame.add(button, BorderLayout.SOUTH);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setLocation(100, 100);
        frame.pack();
        frame.setVisible(true);
        Element paragraph = textArea.getDocument().getDefaultRootElement();
        int contentCount = paragraph.getElementCount();
        for (int i = 0; i < contentCount; i++) {
            Element e = paragraph.getElement(i);
            int rangeStart = e.getStartOffset();
            int rangeEnd = e.getEndOffset();
            String line;
            try {
                line = textArea.getText(rangeStart, rangeEnd - rangeStart);
                System.out.println(line);
            } catch (BadLocationException ex) {
                Logger.getLogger(ResizeJTextArea.class.getName()).log(Level.SEVERE, null, ex);
            }
        }
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                ResizeJTextArea fs = new ResizeJTextArea();
            }
        });
    }
}