java - JTextArea - 仅在文档​​末尾启用编辑

Question

我使用 JTextArea，通过双击我可以在任何地方选择单词，但我不想启用编辑。这意味着文本只能在文本区域的末尾输入，不能在中间的任何位置输入。

我试过像下面这样的鼠标监听器:

@Override
public void mouseClicked(MouseEvent me) {
       if(SwingUtilities.isLeftMouseButton(me)){
        System.err.println("clicked");
        int pos = textArea.getCaretPosition();
        if(pos < textArea.getDocument().getLength()){
            textArea.setCaretPosition(textArea.getDocument().getLength());
        }
    }
   }

这使得双击不选择单词。我了解这是因为插入符号位置已移至末尾。但我怎样才能做到这一点？

Answer 1

查看 Protected Text Component这使您可以保护文档的多个区域免受更改。

或者如果您不需要能够“选择”任何 protected 文本，那么更简单的解决方案是使用 NavigationFilter:

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

public class NavigationFilterPrefixWithBackspace extends NavigationFilter
{
    private int prefixLength;
    private Action deletePrevious;

    public NavigationFilterPrefixWithBackspace(int prefixLength, JTextComponent component)
    {
        this.prefixLength = prefixLength;
        deletePrevious = component.getActionMap().get("delete-previous");
        component.getActionMap().put("delete-previous", new BackspaceAction());
        component.setCaretPosition(prefixLength);
    }

    @Override
    public void setDot(NavigationFilter.FilterBypass fb, int dot, Position.Bias bias)
    {
        fb.setDot(Math.max(dot, prefixLength), bias);
    }

    @Override
    public void moveDot(NavigationFilter.FilterBypass fb, int dot, Position.Bias bias)
    {
        fb.moveDot(Math.max(dot, prefixLength), bias);
    }

    class BackspaceAction extends AbstractAction
    {
        @Override
        public void actionPerformed(ActionEvent e)
        {
            JTextComponent component = (JTextComponent)e.getSource();

            if (component.getCaretPosition() > prefixLength)
            {
                deletePrevious.actionPerformed( null );
            }
        }
    }

    private static void createAndShowUI()
    {
        JTextField textField = new JTextField("Prefix_", 20);
        textField.setNavigationFilter( new NavigationFilterPrefixWithBackspace(7, textField) );

        JFrame frame = new JFrame("Navigation Filter Example");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.getContentPane().add(textField);
        frame.pack();
        frame.setLocationRelativeTo( null );
        frame.setVisible(true);
    }

    public static void main(String[] args)
    {
        SwingUtilities.invokeLater(new Runnable()
        {
            public void run()
            {
                createAndShowUI();
            }
        });
    }
}