Java remove old Highlight

Question

Sorry to be asking this, since there are a few other posts about the same topic, but I just didn't manage to apply those solutions for my issue.

Simple scenario. I have a JTextPane where I have a search method. It detects all matched words and highlights them grey. To navigate through different matches, I have a second Highlighter which highlights the current "active" match red. By pressing buttons the active highlight goes to the next match. (Basically how chromes search works)

Everything works except removing the old active highlighter. There is a method called .removeHighlight() which I would need to remove the old highlight, but no matter what I plug in as parameter, I get either exceptions or nothing happens. I would use .removeAllHighlights() but because I have other highlights( highlighting all hits grey) I would loose them, so I have to only remove the last active highlight. Official oracle docs did something with removeHighlight(hilites[i]) but honestly I have no clue what was going on there. here The code I've got so far:

private DefaultHighlightPainter highlightOne =  new DefaultHighlightPainter(Color.RED);
private Object last;

public void paintAt(int pos){
    try {
        if (last != null){
            motherFrame.tField.getHighlighter().removeHighlight(last);
        }
        last = motherFrame.tField.getHighlighter().addHighlight(pos, pos + searchWordLength, highlightOne);
    } catch (BadLocationException e) {
        //TODO
    }
}  

And here a pic:

UPDATE Here is a runnable: (Sorry for the messy code.)

http://hostcode.sourceforge.net/view/2563 and http://hostcode.sourceforge.net/view/2564

Answer 1

Highlighter#addHighlight returns an Object tag which represents the current highlight. This tag should be used when calling Highlighter#removeHighlight, this, I assume, means you can use the same instance of the HighlightPainter to highlight multiple parts of the document, but still manage them separately, for example...

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.EventQueue;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Rectangle;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.File;
import java.io.FileReader;
import java.io.IOException;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextField;
import javax.swing.JTextPane;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
import javax.swing.text.BadLocationException;
import javax.swing.text.DefaultHighlighter;
import javax.swing.text.Document;

public class TestEditorPane01 {

    public static void main(String[] args) {
        new TestEditorPane01();
    }

    public TestEditorPane01() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                }

                JFrame frame = new JFrame();
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.setLayout(new BorderLayout());
                frame.add(new EditorPane());
                frame.setSize(400, 400);
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);

            }
        });
    }

    public class EditorPane extends JPanel {

        private JTextPane editor = new JTextPane();
        private int lastMatch;
        private String find = "Method";
        private DefaultHighlighter.DefaultHighlightPainter highlightPainter;
        private Object highlightTag;

        private JTextField searchField;
        private JButton searchButton;

        public EditorPane() {
            setLayout(new BorderLayout());
            editor = new JTextPane();
            try (FileReader reader = new FileReader(new File("/some file.txt"))) {
                editor.read(reader, "script");
            } catch (IOException exp) {
                exp.printStackTrace();
            }
            add(new JScrollPane(editor));

            JPanel searchPane = new JPanel(new GridBagLayout());
            searchField = new JTextField(10);
            searchButton = new JButton("Search");
            GridBagConstraints gbc = new GridBagConstraints();
            gbc.gridx = 0;
            gbc.gridy = 0;
            gbc.fill = GridBagConstraints.HORIZONTAL;
            gbc.weightx = 1;
            searchPane.add(searchField, gbc);

            gbc.gridx++;
            gbc.fill = GridBagConstraints.NONE;
            gbc.weightx = 0;
            searchPane.add(searchButton, gbc);

            searchButton.addActionListener(new ActionListener() {

                @Override
                public void actionPerformed(ActionEvent e) {
                    String text = searchField.getText();
                    if (!text.equals(find)) {
                        find = text;
                        lastMatch = 0;
                    }
                    highlightNext();
                }
            });

            add(searchPane, BorderLayout.SOUTH);

        }

        public void highlightNext() {

            Document document = editor.getDocument();
            try {

                if (lastMatch + find.length() >= document.getLength()) {
                    lastMatch = 0;
                }

                for (; lastMatch + find.length() < document.getLength(); lastMatch++) {
                    String match = document.getText(lastMatch, find.length());
                    if (find.equalsIgnoreCase(match)) {
                        if (highlightTag != null) {
                            editor.getHighlighter().removeHighlight(highlightTag);
                        }

                        if (highlightPainter == null) {
                            highlightPainter = new javax.swing.text.DefaultHighlighter.DefaultHighlightPainter(Color.YELLOW);
                        }

                        highlightTag = editor.getHighlighter().addHighlight(lastMatch, lastMatch + find.length(), highlightPainter);

                        Rectangle viewRect = editor.modelToView(lastMatch);
                        editor.scrollRectToVisible(viewRect);

                        lastMatch += find.length();
                        break;
                    }
                }
            } catch (BadLocationException ex) {
                ex.printStackTrace();
            }

        }

    }
}

Since you are doing this, and it's not working, this would suggest that there is something else wrong with your code which is not evident in the snippet you have provided. Consider providing a runnable example which demonstrates your problem. This will result in less confusion and better responses

Updated...

1. Don't link your example code to an external site, not everyone can access external sites or can be bothered to follow links anyway...
2. A runnable example should be self contained and have no reliance on other libraries or resources, like icons and should be contained within a single file
3. Don't expose your UI components unnecessarily, that is, I don't think SearchDialog really needs to know about TestFrame, all it's interested in is the JTextComponent...
4. Your "new" example and your existing code snippet are inconsistent. You are no longer assigning the result of addHighlight to last??
5. Don't use null layouts...

When I finally got your example code to compile, this is what I was presented with...

...Okay, so thought, I'd just expand the window...

...well, there's a problem...which I don't have the time to solve.

Avoid using null layouts, pixel perfect layouts are an illusion within modern ui design. There are too many factors which affect the individual size of components, none of which you can control. Swing was designed to work with layout managers at the core, discarding these will lead to no end of issues and problems that you will spend more and more time trying to rectify

Take a look at Why is it frowned upon to use a null layout in SWING? for more details...

Answer 2

Thanks to MadProgrammer I found out what the problem was:

For the original question "How to remove the old highlighter" the answer is simple: It is the sample code I posted.

private DefaultHighlightPainter highlightOne =  new DefaultHighlightPainter(Color.RED);
private Object last;

public void paintAt(int pos){
    try {
        if (last != null){
            textPane.getHighlighter().removeHighlight(last);
        }
        last = textPane.getHighlighter().addHighlight(pos, pos + searchWordLength, highlightOne);
    } catch (BadLocationException e) {
        //TODO
    }
}  

(Since I have two Highlighter the first one was overwriting the second one, so the second one wasn't showing up. That's why I thought my code was not working.)

For the updated question "How to handle multiple Highlighter" the answer is also simple. There is just one catch to the whole thing one has to know. The paint from the Highlighter does not get over-painted by an other Highlighter which is called later. So basically I had to invert the order of how the Highlighter were called. Which looks something like this:

textPane.getHighlighter().removeAllHighlights();
textPane.getHighlighter().addHighlight(pos, pos + searchWordLength, red);
for int i = 0; i < matchList.size(); i++){
    int position = matchList.get(i);
    textPane.getHighlighter().addHighlight(position, possition + searchWordLength, grey);
}

This is not a optimal solution since you have to repaint every Highlighter with every change. But one could optimize this with an delta-change-draw (only redraw the parts that change).