Highlight JTextArea

Question

i have a problem with:

        int index = text.indexOf(myWord);

        while (index >= 0) {
            int len = pattern.length();
            hl.addHighlight(index, index + len, DefaultHighlighter.DefaultPainter);
            index = text.indexOf(pattern, index + len);
        }

when I reach the end of line highlighting is still enable, how to disable highlight ? The result of above code:

Thanks for answer but the problem is:

The black line is a place where I clicked and start typing, it is just bug.

Answer 1

Well I had to do some assumptions on your variable names and I hope I did it right. Basically your code worked for me but I didn't understand the first line:

int index = text.indexOf(myWord);

I think it should be:

int index = text.indexOf(pattern);

Anyway, I wrote this code and it worked for me:

String pattern = "<aa>";
String text = textArea.getText();        
int index = text.indexOf(pattern);
while(index >= 0){
    try {                
        hl.addHighlight(index, index + pattern.length(), DefaultHighlighter.DefaultPainter);
        index = text.indexOf(pattern, index + pattern.length());            
    } catch (BadLocationException ex) {
        ex.printStackTrace();
    }
}

---

Update

Look when you click on the end of marked text and start typing the text will be also marked- it is a my bug.

Sorry I didn't see that before. I don't think you can stop a highlighter but you can make it using a CaretListener and doing the stuff there. This way if you input a new string that matches your pattern it will be highlighted too:

textArea.addCaretListener(new CaretListener() {            
    @Override
    public void caretUpdate(CaretEvent e) {
        if(e.getMark() == e.getDot()){
            Highlighter hl = textArea.getHighlighter();
            hl.removeAllHighlights();

            String pattern = "<aa>";
            String text = textArea.getText();        
            int index = text.indexOf(pattern);
            while(index >= 0){
                try {                
                    Object o = hl.addHighlight(index, index + pattern.length(), DefaultHighlighter.DefaultPainter);
                    index = text.indexOf(pattern, index + pattern.length());
                } catch (BadLocationException ex) {
                    ex.printStackTrace();
                }
            }
        }
    }
});

Note e.getMark() == e.getDot() means "there's no text selection" based on CaretEvent.getDot() and CaretEvent.getMark() javadoc. Otherwise you shouldn't highlight anything but selected text.

Screenshot

Updated SSCCE

Here's a complete SSCCE to test it:

import java.awt.Dimension;
import java.awt.FlowLayout;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.SwingUtilities;
import javax.swing.event.CaretEvent;
import javax.swing.event.CaretListener;
import javax.swing.text.BadLocationException;
import javax.swing.text.DefaultHighlighter;
import javax.swing.text.Highlighter;

public class Demo {

    private void initGUI(){

        final JTextArea textArea = new JTextArea();

        textArea.addCaretListener(new CaretListener() {            
            @Override
            public void caretUpdate(CaretEvent e) {
                if(e.getMark() == e.getDot()){
                    Highlighter hl = textArea.getHighlighter();
                    hl.removeAllHighlights();

                    String pattern = "<aa>";
                    String text = textArea.getText();        
                    int index = text.indexOf(pattern);
                    while(index >= 0){
                        try {                
                            Object o = hl.addHighlight(index, index + pattern.length(), DefaultHighlighter.DefaultPainter);
                            index = text.indexOf(pattern, index + pattern.length());
                        } catch (BadLocationException ex) {
                            ex.printStackTrace();
                        }
                    }
                }
            }
        });

        JScrollPane scrollPane = new JScrollPane(textArea);
        scrollPane.setPreferredSize(new Dimension(300,200));

        JPanel content = new JPanel(new FlowLayout());
        content.add(scrollPane);

        JFrame frame = new JFrame("Demo");
        frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
        frame.setContentPane(content);
        frame.pack();
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);        
    }


    public static void main(String[] args) {        
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                new Demo().initGUI();
            }
        });
    }

}