Java selected text over highlighted text

Question

I have a text JTextArea that has some highlighted text using:

inputTextArea.getHighlighter().addHighlight(start, end, new DefaultHighlighter.DefaultHighlightPainter(new Color(color)));

It works well but then but If I select some text using the mouse, the selection is not painted when it is over the highlighted text.

So for example If I just want to select a part of the highlighted text, I can't see the selection.

How can I do to make the selection appear over the highlight?

maybe you need to use a caretListener to update the highlighted text - https://stackoverflow.com/questions/9242620/detecting-text-selection-in-jtextarea — Mauricio Gracia Gutierrez, Apr 13 '18 at 13:31

score 2 · Answer 1 · answered Apr 13 '18 at 14:21

You simply need a proxy highlighter which allows to modify painting coordinates. Here is an example:

import java.awt.Color;
import java.awt.Graphics;
import java.awt.Shape;

import javax.swing.JFrame;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.WindowConstants;
import javax.swing.text.DefaultHighlighter;
import javax.swing.text.Highlighter.HighlightPainter;
import javax.swing.text.JTextComponent;


public class HighlightTest {

    public static void main(String[] args) {
        JTextArea textArea = new JTextArea(10, 30);
        textArea.setText("It's a small test to understand whether proxy works or not.");
        try {
            textArea.getHighlighter().addHighlight(5, 15,
                    new ProxyHighlightPainer(new DefaultHighlighter.DefaultHighlightPainter(Color.RED)));
        } catch (Exception e) {
            // add something when required
        }
        textArea.addCaretListener(e -> textArea.repaint()); // must provoke repaint of highlighter
        JFrame frm = new JFrame("Test");
        frm.add(new JScrollPane(textArea));
        frm.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
        frm.pack();
        frm.setLocationRelativeTo(null);
        frm.setVisible(true);
    }
    private static class ProxyHighlightPainer implements HighlightPainter {

        private final HighlightPainter delegate;

        public ProxyHighlightPainer(HighlightPainter delegate) {
            this.delegate = delegate;
        }

        @Override
        public void paint(Graphics g, int p0, int p1, Shape bounds, JTextComponent c) {
            int startSel = c.getSelectionStart();
            int endSel = c.getSelectionEnd();
            if (startSel == endSel || startSel >= p1 || endSel <= p0) {
                // no selection or no intersection: paint normal
                delegate.paint(g, p0, p1, bounds, c);
            } else if (startSel >= p0 && endSel >= p1) {
                delegate.paint(g, p0, startSel, bounds, c);
            } else if (startSel <= p0 && endSel <= p1) {
                delegate.paint(g, endSel, p1, bounds, c);
            } else if (startSel <= p0 && endSel <= p1) {
                delegate.paint(g, p0, startSel, bounds, c);
                delegate.paint(g, endSel, p1, bounds, c);
            } else {
                // just to be safe
                delegate.paint(g, p0, p1, bounds, c);
            }
        }

    }
}

(1+) nice solution. I've never understood why this isn't the default behaviour. — camickr, Apr 13 '18 at 15:15

camickr · Accepted Answer · 2018-04-13T15:20:35.277

You might be able to use:

JTextArea textArea = new JTextArea(10, 20);
textArea.setText( "one\ntwo\nthree\nfour\nfive\nsix\nseven\neight" );

DefaultHighlighter highlighter =  (DefaultHighlighter)textArea.getHighlighter();
highlighter.setDrawsLayeredHighlights(false);

try
{
    highlighter.addHighlight(10, 20, new DefaultHighlighter.DefaultHighlightPainter(Color.YELLOW));
}
catch(Exception e) {}

Changing the layered highlights property has two effects:

You will now see the selection
Highlighting is done to the end of the text area for a line, (not just to the end of the text) when highlighted text spans multiple lines.

Java selected text over highlighted text

2 Answers2