JTextArea - 如何在指定偏移处设置文本？

Question

I want to set some text at a specified offset in my JTextArea . Let's say I have already in my edit "aaa bbb" and I want to overwrite "bbb" with "house", how can I do that in Java?

Answer 1

You could use replaceRange()

public void replaceRange(String str, int start, int end)

Replaces text from the indicated start to end position with the new text specified. Does nothing if the model is null. Simply does a delete if the new string is null or empty.

This method is thread safe, although most Swing methods are not. Please see Threads and Swing for more information.

Answer 2

You need to take a look at three methods setSelectionStart(...) , setSelectionEnd(...) and replaceSelection(...) .

Here is a small sample program to help your cause:

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class TextAreaSelection
{
    private JTextField replaceTextField;
    private JTextField startIndexField;
    private JTextField endIndexField;

    private void createAndDisplayGUI()
    {
        final JFrame frame = new JFrame("JTextArea Selection");
        frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
        frame.setLocationByPlatform(true);

        JPanel contentPane = new JPanel();
        contentPane.setLayout(new BorderLayout(5, 5));
        contentPane.setOpaque(true);

        final JTextArea tarea = new JTextArea(10, 10);
        tarea.setText("aaa bbb");

        final JButton updateButton = new JButton("UPDATE TEXT");
        updateButton.addActionListener(new ActionListener()
        {
            public void actionPerformed(ActionEvent ae)
            {
                //tarea.setSelectionStart(4);
                //tarea.setSelectionEnd(7);
                //tarea.replaceSelection("house");
                int selection = JOptionPane.showConfirmDialog(null, getPanel());
                if (selection == JOptionPane.OK_OPTION)
                {
                    if (replaceTextField.getDocument().getLength() > 0
                        && startIndexField.getDocument().getLength() > 0
                        && endIndexField.getDocument().getLength() > 0)
                    {   
                        String text = replaceTextField.getText().trim();
                        int start = Integer.parseInt(startIndexField.getText().trim());
                        int end = Integer.parseInt(endIndexField.getText().trim());
                        tarea.replaceRange(text, start, end);
                    }
                }
            }
        });

        contentPane.add(tarea, BorderLayout.CENTER);
        contentPane.add(updateButton, BorderLayout.PAGE_END);

        frame.getContentPane().add(contentPane);
        frame.pack();
        frame.setVisible(true);
    }

    private JPanel getPanel()
    {
        JPanel panel = new JPanel();
        panel.setLayout(new GridLayout(0, 2, 2, 2));

        JLabel replaceLabel = new JLabel("Enter new String : "
                                                , JLabel.CENTER);
        replaceTextField = new JTextField(10);

        JLabel startIndexLabel = new JLabel("Enter Start Index : "
                                                , JLabel.CENTER);
        startIndexField = new JTextField(10);   

        JLabel endIndexLabel = new JLabel("Enter End Index : ");
        endIndexField = new JTextField(10); 

        panel.add(replaceLabel);
        panel.add(replaceTextField);
        panel.add(startIndexLabel);
        panel.add(startIndexField);
        panel.add(endIndexLabel);
        panel.add(endIndexField);

        return panel;
    }

    public static void main(String... args)
    {
        SwingUtilities.invokeLater(new Runnable()
        {
            public void run()
            {
                new TextAreaSelection().createAndDisplayGUI();
            }
        });
    }
}