How to change the color of specific words in a JTextPane?

Question

How do I change the color of specific words in a JTextPane just while the user is typing? Should I override JTextPane paintComponent method?

Answer 1

No. You are not supposed to override the paintComponent() method. Instead, you should use StyledDocument. You should also delimit the words by your self.

Here is the demo, which turns "public", "protected" and "private" to red when typing, just like a simple code editor:

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

public class Test extends JFrame {
    private int findLastNonWordChar (String text, int index) {
        while (--index >= 0) {
            if (String.valueOf(text.charAt(index)).matches("\\W")) {
                break;
            }
        }
        return index;
    }

    private int findFirstNonWordChar (String text, int index) {
        while (index < text.length()) {
            if (String.valueOf(text.charAt(index)).matches("\\W")) {
                break;
            }
            index++;
        }
        return index;
    }

    public Test () {
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        setSize(400, 400);
        setLocationRelativeTo(null);

        final StyleContext cont = StyleContext.getDefaultStyleContext();
        final AttributeSet attr = cont.addAttribute(cont.getEmptySet(), StyleConstants.Foreground, Color.RED);
        final AttributeSet attrBlack = cont.addAttribute(cont.getEmptySet(), StyleConstants.Foreground, Color.BLACK);
        DefaultStyledDocument doc = new DefaultStyledDocument() {
            public void insertString (int offset, String str, AttributeSet a) throws BadLocationException {
                super.insertString(offset, str, a);

                String text = getText(0, getLength());
                int before = findLastNonWordChar(text, offset);
                if (before < 0) before = 0;
                int after = findFirstNonWordChar(text, offset + str.length());
                int wordL = before;
                int wordR = before;

                while (wordR <= after) {
                    if (wordR == after || String.valueOf(text.charAt(wordR)).matches("\\W")) {
                        if (text.substring(wordL, wordR).matches("(\\W)*(private|public|protected)"))
                            setCharacterAttributes(wordL, wordR - wordL, attr, false);
                        else
                            setCharacterAttributes(wordL, wordR - wordL, attrBlack, false);
                        wordL = wordR;
                    }
                    wordR++;
                }
            }

            public void remove (int offs, int len) throws BadLocationException {
                super.remove(offs, len);

                String text = getText(0, getLength());
                int before = findLastNonWordChar(text, offs);
                if (before < 0) before = 0;
                int after = findFirstNonWordChar(text, offs);

                if (text.substring(before, after).matches("(\\W)*(private|public|protected)")) {
                    setCharacterAttributes(before, after - before, attr, false);
                } else {
                    setCharacterAttributes(before, after - before, attrBlack, false);
                }
            }
        };
        JTextPane txt = new JTextPane(doc);
        txt.setText("public class Hi {}");
        add(new JScrollPane(txt));
        setVisible(true);
    }

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

The code is not so beautiful since I typed it quickly but it works. And I hope it will give you some hint.

Answer 2

Overwriting paintComponent will not help you.

This is not an easy one, but not impossible either. Something like this will help you:

DefaultStyledDocument document = new DefaultStyledDocument();
JTextPane textpane = new JTextPane(document);
StyleContext context = new StyleContext();
// build a style
Style style = context.addStyle("test", null);
// set some style properties
StyleConstants.setForeground(style, Color.BLUE);
// add some data to the document
document.insertString(0, "", style);

You may need to tweak this, but at least it shows you where to start.

Answer 3

Another solution is to use a DocumentFilter.

Here is an example:

Create a class that extends DocumentFilter:

private final class CustomDocumentFilter extends DocumentFilter
{
        private final StyledDocument styledDocument = yourTextPane.getStyledDocument();

        private final StyleContext styleContext = StyleContext.getDefaultStyleContext();
        private final AttributeSet greenAttributeSet = styleContext.addAttribute(styleContext.getEmptySet(), StyleConstants.Foreground, Color.GREEN);
        private final AttributeSet blackAttributeSet = styleContext.addAttribute(styleContext.getEmptySet(), StyleConstants.Foreground, Color.BLACK);

    // Use a regular expression to find the words you are looking for
    Pattern pattern = buildPattern();

    @Override
    public void insertString(FilterBypass fb, int offset, String text, AttributeSet attributeSet) throws BadLocationException {
        super.insertString(fb, offset, text, attributeSet);

        handleTextChanged();
    }

    @Override
    public void remove(FilterBypass fb, int offset, int length) throws BadLocationException {
        super.remove(fb, offset, length);

        handleTextChanged();
    }

    @Override
    public void replace(FilterBypass fb, int offset, int length, String text, AttributeSet attributeSet) throws BadLocationException {
        super.replace(fb, offset, length, text, attributeSet);

        handleTextChanged();
    }

    /**
     * Runs your updates later, not during the event notification.
     */
    private void handleTextChanged()
    {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                updateTextStyles();
            }
        });
    }

    /**
     * Build the regular expression that looks for the whole word of each word that you wish to find.  The "\\b" is the beginning or end of a word boundary.  The "|" is a regex "or" operator.
     * @return
     */
    private Pattern buildPattern()
    {
        StringBuilder sb = new StringBuilder();
        for (String token : ALL_WORDS_THAT_YOU_WANT_TO_FIND) {
            sb.append("\\b"); // Start of word boundary
            sb.append(token);
            sb.append("\\b|"); // End of word boundary and an or for the next word
        }
        if (sb.length() > 0) {
            sb.deleteCharAt(sb.length() - 1); // Remove the trailing "|"
        }

        Pattern p = Pattern.compile(sb.toString());

        return p;
    }


    private void updateTextStyles()
    {
        // Clear existing styles
        styledDocument.setCharacterAttributes(0, yourTextPane.getText().length(), blackAttributeSet, true);

        // Look for tokens and highlight them
        Matcher matcher = pattern.matcher(yourTextPane.getText());
        while (matcher.find()) {
            // Change the color of recognized tokens
            styledDocument.setCharacterAttributes(matcher.start(), matcher.end() - matcher.start(), greenAttributeSet, false);
        }
    }
}

All you need to do then is apply the DocumentFilter that you created to your JTextPane as follows:

((AbstractDocument) yourTextPane.getDocument()).setDocumentFilter(new CustomDocumentFilter());

Answer 4

You can extend DefaultStyledDocument like I did here for an SQL editor I am building with keyword text coloring ...

    import java.util.ArrayList;
    import java.util.List;
    import javax.swing.text.AttributeSet;
    import javax.swing.text.BadLocationException;
    import javax.swing.text.DefaultStyledDocument;
    import javax.swing.text.Style;

    public class KeywordStyledDocument extends DefaultStyledDocument  {
        private static final long serialVersionUID = 1L;
        private Style _defaultStyle;
        private Style _cwStyle;

        public KeywordStyledDocument(Style defaultStyle, Style cwStyle) {
            _defaultStyle =  defaultStyle;
            _cwStyle = cwStyle;
        }

         public void insertString (int offset, String str, AttributeSet a) throws BadLocationException {
             super.insertString(offset, str, a);
             refreshDocument();
         }

         public void remove (int offs, int len) throws BadLocationException {
             super.remove(offs, len);
             refreshDocument();
         }

         private synchronized void refreshDocument() throws BadLocationException {
             String text = getText(0, getLength());
             final List<HiliteWord> list = processWords(text);

             setCharacterAttributes(0, text.length(), _defaultStyle, true);   
             for(HiliteWord word : list) {
                 int p0 = word._position;
                 setCharacterAttributes(p0, word._word.length(), _cwStyle, true);
             }
         }       

         private static  List<HiliteWord> processWords(String content) {
             content += " ";
             List<HiliteWord> hiliteWords = new ArrayList<HiliteWord>();
             int lastWhitespacePosition = 0;
             String word = "";
             char[] data = content.toCharArray();

             for(int index=0; index < data.length; index++) {
                 char ch = data[index];
                 if(!(Character.isLetter(ch) || Character.isDigit(ch) || ch == '_')) {
                     lastWhitespacePosition = index;
                     if(word.length() > 0) {
                         if(isReservedWord(word)) {
                             hiliteWords.add(new HiliteWord(word,(lastWhitespacePosition - word.length())));
                         }
                         word="";
                     }
                 }
                 else {
                     word += ch;
                 }
            }
            return hiliteWords;
         }

         private static final boolean isReservedWord(String word) {
             return(word.toUpperCase().trim().equals("CROSS") || 
                            word.toUpperCase().trim().equals("CURRENT_DATE") ||
                            word.toUpperCase().trim().equals("CURRENT_TIME") ||
                            word.toUpperCase().trim().equals("CURRENT_TIMESTAMP") ||
                            word.toUpperCase().trim().equals("DISTINCT") ||
                            word.toUpperCase().trim().equals("EXCEPT") ||
                            word.toUpperCase().trim().equals("EXISTS") ||
                            word.toUpperCase().trim().equals("FALSE") ||
                            word.toUpperCase().trim().equals("FETCH") ||
                            word.toUpperCase().trim().equals("FOR") ||
                            word.toUpperCase().trim().equals("FROM") ||
                            word.toUpperCase().trim().equals("FULL") ||
                            word.toUpperCase().trim().equals("GROUP") ||
                            word.toUpperCase().trim().equals("HAVING") ||
                            word.toUpperCase().trim().equals("INNER") ||
                            word.toUpperCase().trim().equals("INTERSECT") ||
                            word.toUpperCase().trim().equals("IS") ||
                            word.toUpperCase().trim().equals("JOIN") ||
                            word.toUpperCase().trim().equals("LIKE") ||
                            word.toUpperCase().trim().equals("LIMIT") ||
                            word.toUpperCase().trim().equals("MINUS") ||
                            word.toUpperCase().trim().equals("NATURAL") ||
                            word.toUpperCase().trim().equals("NOT") ||
                            word.toUpperCase().trim().equals("NULL") ||
                            word.toUpperCase().trim().equals("OFFSET") ||
                            word.toUpperCase().trim().equals("ON") ||
                            word.toUpperCase().trim().equals("ORDER") ||
                            word.toUpperCase().trim().equals("PRIMARY") ||
                            word.toUpperCase().trim().equals("ROWNUM") ||
                            word.toUpperCase().trim().equals("SELECT") ||
                            word.toUpperCase().trim().equals("SYSDATE") ||
                            word.toUpperCase().trim().equals("SYSTIME") ||
                            word.toUpperCase().trim().equals("SYSTIMESTAMP") ||
                            word.toUpperCase().trim().equals("TODAY") ||
                            word.toUpperCase().trim().equals("TRUE") ||
                            word.toUpperCase().trim().equals("UNION") ||
                            word.toUpperCase().trim().equals("UNIQUE") ||
                            word.toUpperCase().trim().equals("WHERE"));
        }
    }

Simply add it to your class like so:

    import java.awt.BorderLayout;
    import java.awt.Color;
    import java.awt.Font;
    import javax.swing.JFrame;
    import javax.swing.JScrollPane;
    import javax.swing.JTextPane;
    import javax.swing.text.BadLocationException;
    import javax.swing.text.Style;
    import javax.swing.text.StyleConstants;
    import javax.swing.text.StyleContext;

    public class SQLEditor extends JFrame {
        private static final long serialVersionUID = 1L;

        public SQLEditor() {
            StyleContext styleContext = new StyleContext();
            Style defaultStyle = styleContext.getStyle(StyleContext.DEFAULT_STYLE);
            Style cwStyle = styleContext.addStyle("ConstantWidth", null);
            StyleConstants.setForeground(cwStyle, Color.BLUE);
            StyleConstants.setBold(cwStyle, true);

            final JTextPane pane = new JTextPane(new KeywordStyledDocument(defaultStyle, cwStyle));
            pane.setFont(new Font("Courier New", Font.PLAIN, 12));

            JScrollPane scrollPane = new JScrollPane(pane);
            getContentPane().add(scrollPane, BorderLayout.CENTER);
            setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
            setSize(375, 400);      
        }

        public static void main(String[] args) throws BadLocationException {
            SQLEditor app = new SQLEditor();
            app.setVisible(true);
        }
    }

Here's the missing HiliteWord class ...

public class HiliteWord {

    int _position;  
    String _word;

    public HiliteWord(String word, int position) {
        _position = position;   
        _word = word;
    }
}

Answer 5

@Constantin

Dear Constantin, I used Your fine Solution for my little Project and after only a few Adjustments your solution worked well for me.

If you allow, my Changes were:

My Use of your Class KeywordStyledDocument in my own JFrame:

StyleContext styleContext = new StyleContext();
Style defaultStyle = styleContext.getStyle(StyleContext.DEFAULT_STYLE);

This line I Have changed: MutableAttributeSet cwStyle = Functions.style(true, false, Color.RED);

private JTextPane jTextPaneNumbers = new JTextPane(new KeywordStyledDocument(defaultStyle, cwStyle));

I outsourced the supply of the cwStyle Instance in a static Function called style:

public static MutableAttributeSet style(boolean boldness, boolean italic, Color color) {
    
    MutableAttributeSet s = new SimpleAttributeSet();
    
    StyleConstants.setLineSpacing(s, -0.2f);
    StyleConstants.setBold(s, boldness);
    StyleConstants.setItalic(s, italic);
    StyleConstants.setForeground(s, color);
    
    return s;
}

Furthermore as you see above the cwStyle Class is not longer an Instance of StyleConstants but an Inctance of MutableAttributeSet. Therefore naturally I had to change the Constructor of your KeywordStyledDocumentClass as well:

public KeywordStyledDocument(Style defaultStyle, MutableAttributeSet cwStyle) {
    _defaultStyle =  defaultStyle;
    _cwStyle = cwStyle;
}

After this litle changes and adding my own "words" in your isReservedWord Function and add my Characters ' and * to your processWord Function:

 ...word.toUpperCase().trim().equals("UNION") ||
                    word.toUpperCase().trim().equals("UNIQUE") ||
                    word.toUpperCase().trim().equals("WHERE") ||
                    word.trim().equals("''''''") ||
                    word.trim().equals("******") 
                    );
 if(!(Character.isLetter(ch) || Character.isDigit(ch) || ch == '_' || ch == '\'' || ch == '*')) {

I became my whished Result:

Thank you very much for showing your Code here.