How highlighter of Java Swing works on marginal cases?

Question

I have this code :

JTextArea textComp;

Highlighter hilite = textComp.getHighlighter();

if (word.toString().equals(pattern[i])) 
{
    hilite.addHighlight(posStart, (posEnd), myHighlighter);
    break;
}

word is a StringBuilder

Suppose the condition in if matches and hilite.addHighlight(posStart, (posEnd), myHighlighter); - this statement is going to execute. Then the textComp contains

int myVar

And I try to highlight like this

int myVar

At that time, posStart = 0 and posEnd = 3. But As I am entering something into the textArea the highlighter is extending itself to the end like this:

int myVar

Can anyone help me with this?

And if I make the statement:

hilite.addHighlight(posStart, (posEnd-1), myHighlighter);

Then with posStart=0, posEnd=3, then only

*in*t myVar this happens. i.e "in" is highlighted but "t" is not!

EDIT The function:

Highlighter.HighlightPainter myHighlighter = new MyHighlightPainter(
                    Color.LIGHT_GRAY);

            try {
                Highlighter hilite = textComp.getHighlighter();
                Document doc = textComp.getDocument();
                String text = doc.getText(0, doc.getLength());
                String[] words = text.split(" ");

                                int posEnd, posStart = 0;
                while (text.length() > posStart) {
                    posEnd = posStart;
                    StringBuilder word = new StringBuilder();
                    while (posEnd < text.length() && text.charAt(posEnd) != ' ') {
                        word.append(text.charAt(posEnd++));
                    }
                    for (int i = 0; i < pattern.length; i++) {

                        if (word.toString().equals(pattern[i])) {
                            hilite.addHighlight(posStart, (posEnd-1), myHighlighter);
                            break;
                        }

                    }
                    posStart = posStart + posEnd + 1;
                }
            } catch (BadLocationException e) {
            }

Answer 1

I have done this to solve the problem:

int wordEnd = 0, wordStart = 0;




Highlighter hilite = textComp.getHighlighter();
                        Document doc = textComp.getDocument();
                        String text = doc.getText(0, doc.getLength());

                        while (text.length() > wordEnd) 
                        {
                            String word = new String();
                            if(text.charAt(wordEnd) == ' ')
                            {
                                word = text.substring(wordStart, wordEnd);
                                for (int i = 0; i < pattern.length; i++) 
                                {
                                        if (word.toString().equals(pattern[i])) 
                                        {
                                            hilite.addHighlight(wordStart, (wordEnd), myHighlighter);

                                            break;
                                        }
                                }
                                wordStart = wordEnd + 1;
                            }
                            wordEnd++;
                        }

What I did, is to getting a word by detecting a space after it(you can extend the logic) and then highlighting the previous word. This is continuous all through typing.

Answer 2

actually I was wondering how this Highlighter works!

Yes the API is confusing. I believe the first index is meant to be inclusive and the last index exclusive.

Whenever I highlight when searching for a word I use code like:

String text = "one two three four...";
String search "three";

int offset = text.indexOf(search);

if (offset != -1)
    textPane.getHighlighter().addHighlight(offset, offset + search.length(), painter);

Answer 3

Your issue seems to not really be how the highlighter highlights text, but rather how the highlight changes as the text is edited. You can deal with this by adding a change listener to the TextArea, and adjusting the affected highlights (using changeHighlight()) as needed.