Custom StyledEditorKit: simple example/tutorial?

Question

I'm trying to write a simple EditorKit to color specific parts of a text (and later different fonts). I extended StyledEditorKit for this, but can't get any text to be colored in my JTextPane. The Java Tutorial and also what I've found in this forum and google didn't show how to start writing a simple EditorKit.

Answer 1

Well, I have a simple example that shows how to start. Of course it's brute force colorizing always the complete text and only works for well-formed XML, but it's a working example of how to write your own EditorKit. It shows that only a few things have to be done.
public class XMLEditorKit extends StyledEditorKit {
     * Constructor.
    public XMLEditorKit() {
        super();
    }//XMLEditorKit()
     * Overwrites super.
    public String getContentType() {
        return "text/xml";
    }//getContentType()
     * Overwrites super.
    public Document createDefaultDocument() {
        return new XMLDocument();
    }//createDefaultDocument()
}//XMLEditorKit
class XMLDocument extends DefaultStyledDocument {
    /** Attributes for XML element tag. */
    private MutableAttributeSet tag = null;
    /** Attributes for element value. */
    private MutableAttributeSet elementValue = null;
     * Constructor.
    public XMLDocument() {
        tag = new SimpleAttributeSet();
        StyleConstants.setForeground(tag, Color.blue);
        elementValue = new SimpleAttributeSet();
        StyleConstants.setForeground(elementValue, Color.black);
    }//XMLDocument()
     * Override AbstractDocument.
    public void insertString(int offset, String str, AttributeSet a) throws BadLocationException {
        super.insertString(offset, str, a);
        colorize();
    }//insertString()
     * Override AbstractDocument.
    public void remove(int offset, int length) throws BadLocationException {
        super.remove(offset, length);
        colorize();
    }//remove()
     * Called when document content changed to revalidate syntax highlightning.
     * Only works correctly for well-formed XML.
    private void colorize() throws BadLocationException {
        String text = getText(0, getLength());
        int startIndex = 0;
        int endIndex = text.length() + 1;
        int openIndex = 0;
        int closeIndex = 0;
        boolean outOfTag = true;
        while (startIndex <= endIndex) {
            openIndex  = text.indexOf('<', startIndex); //next '<'
            closeIndex = text.indexOf('>', startIndex); //next '>'
            if (outOfTag) {
                if (openIndex >= 0) {
                    setCharacterAttributes(startIndex, openIndex - startIndex, elementValue, false);
                    startIndex = openIndex;
                    outOfTag = false;
                } else {
                    setCharacterAttributes(startIndex, endIndex + 1, elementValue, false);
                    break;
            } else { //withinTag
                if (closeIndex >= 0) {                       
                    setCharacterAttributes(startIndex, closeIndex - startIndex + 1, tag, false);
                    startIndex = closeIndex + 1;
                    outOfTag = true;
                } else {
                    setCharacterAttributes(startIndex, endIndex + 1, tag, false);
                    break;
            }//next occurence
    }//colorize()
}//XMLDocumentSo, to start write a custom EditorKit,
1. extend StyledEditorKit (or DefaultEditorKit, if you like)
2. create a document class extending DefaultStyledDocument
3. overwrite insertString()/remove() in your document class to implement your custom text styling.