JTextArea - selection behavior on double / triple click + moving mouse

问题

The problem: when you double click on word in JTextArea it is marked, but when you don't release the mouse button and try to mark next word, it is not marking whole word, but single characters instead.

It should mark the whole words (not single characters) when moving mouse (on double click). That's literally the default behavior in all programs which I tried, like: Notepad, Firefox, Chrome, Word, even Netbeans, etc.

Same thing with triple click (when holding and moving the mouse should mark the next line, not characters).

Any ideas? I had hard time Googling this, but since it's a very common thing I believe there must be a simple option or at least someone already have a solution.

Sample code:

public class TestJTextArea
 {
    public static void main(final String[] args)
    {
        final JPanel panel = new JPanel(new BorderLayout());
        panel.setPreferredSize(new Dimension(500, 500));
        panel.add(new JTextArea(), BorderLayout.CENTER);

        final JFrame frame = new JFrame("Test");
        frame.getContentPane().add(panel, BorderLayout.CENTER);
        frame.pack();
        frame.setResizable(false);
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    }
}

回答1:

Maybe you need to create a customized Caret, for example:

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

public class TestJTextArea2 {
  public Component makeUI() {
    String text = "The quick brown fox jumps over the lazy dog.";
    JTextArea textArea1 = new JTextArea("default\n" + text);
    JTextArea textArea2 = new JTextArea("setCaret\n" + text) {
      @Override public void updateUI() {
        setCaret(null);
        super.updateUI();
        Caret oldCaret = getCaret();
        int blinkRate = oldCaret.getBlinkRate();
        Caret caret = new SelectWordCaret();
        caret.setBlinkRate(blinkRate);
        setCaret(caret);
      }
    };
    JPanel p = new JPanel(new GridLayout(2, 1));
    p.add(new JScrollPane(textArea1));
    p.add(new JScrollPane(textArea2));
    return p;
  }

  public static void main(String[] args) {
    EventQueue.invokeLater(() -> {
      JFrame f = new JFrame();
      f.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
      f.getContentPane().add(new TestJTextArea2().makeUI());
      f.setSize(320, 240);
      f.setLocationRelativeTo(null);
      f.setVisible(true);
    });
  }
}

class SelectWordCaret extends DefaultCaret {
  private boolean wordSelectingMode = false;
  private int p0; // = Math.min(getDot(), getMark());
  private int p1; // = Math.max(getDot(), getMark());

  @Override public void mousePressed(MouseEvent e) {
    super.mousePressed(e);
    int nclicks = e.getClickCount();
    if (SwingUtilities.isLeftMouseButton(e) && !e.isConsumed() && nclicks == 2) {
      p0 = Math.min(getDot(), getMark());
      p1 = Math.max(getDot(), getMark());
      wordSelectingMode = true;
    } else {
      wordSelectingMode = false;
    }
  }

  @Override public void mouseDragged(MouseEvent e) {
    if (wordSelectingMode && !e.isConsumed() && SwingUtilities.isLeftMouseButton(e)) {
      continuouslySelectWords(e);
    } else {
      super.mouseDragged(e);
    }
  }

  private void continuouslySelectWords(MouseEvent e) {
    Position.Bias[] biasRet = new Position.Bias[1];
    JTextComponent c = getComponent();
    int pos = c.getUI().viewToModel2D(c, e.getPoint(), biasRet);
    if(biasRet[0] == null) {
      biasRet[0] = Position.Bias.Forward;
    }
    try {
      if (p0 <= pos && pos <= p1) {
        setDot(p0);
        moveDot(p1, biasRet[0]);
      } else if (p1 < pos) {
        setDot(p0);
        moveDot(Utilities.getWordEnd(c, pos - 1), biasRet[0]);
      } else if (p0 > pos) {
        setDot(p1);
        moveDot(Utilities.getWordStart(c, pos), biasRet[0]);
      }
    } catch (BadLocationException bl) {
      UIManager.getLookAndFeel().provideErrorFeedback(c);
    }
  }
}

来源：https://stackoverflow.com/questions/58690711/jtextarea-selection-behavior-on-double-triple-click-moving-mouse