Highlight Text In JTextArea In Presence of Duplicate Lines

Question

I have a JTextArea which consists of lines (some of them possibly duplicates of one another). I've a requirement where I've to highlight the selected line upon right-click. The code that I'm using to highlight is as follows:

String highlightedText = textArea.getSelectedText();
if(highlightedText != null)
{
   try{
      int index = textArea.getText().indexOf(highlightedText, textArea.getCaretPosition());
      textArea.getHighlighter().addHighlight(index - 1, index + highlightedText.length(),
      new DefaultHighlighter.DefaultHighlightPainter(Color.ORANGE));
   }catch (BadLocationException ex) {           
   }
}

While the highlight upon right-click works, the problem is I cannot get the index of the selected line in the presence of duplicates. So if there're lines like

AAAA
BBBB
AAAA
CCCC
DDDD
AAAA

I cannot get the index of the second "AAAA" when the user tries to highlight this particular line. Can someone help me out with an idea/suggestion to work this this? Thanks!

What you should be aiming at is [modelToView(...) and viewToModel(...)](http://docs.oracle.com/javase/7/docs/api/javax/swing/plaf/TextUI.html). Try this [second example](http://stackoverflow.com/questions/10306901/how-to-change-highlighting-color-in-java-swing-textarea-and-also-change-the-be/10309277#10309277) having used both the said methods (scroll to the second example.) — nIcE cOw, Jun 15 '12 at 15:58
Try this example, which resembles your case regarding [clicking a particular location of the `JTextArea` and finding it's location, using above mentioned methods](http://stackoverflow.com/questions/10462725/actionlistener-for-a-specific-text-inside-a-jtextarea/10463120#10463120) — nIcE cOw, Jun 15 '12 at 16:04
Using `viewToModel()` you can get an offset value, as shown in the above link, which can give you the LineNumber using this method [getLineOfOffset(...)](http://docs.oracle.com/javase/7/docs/api/javax/swing/JTextArea.html#getLineOfOffset(int)). Nice question though, wanted to upvote this, but my limit is gone for today, so will do that in eight hours :-) — nIcE cOw, Jun 15 '12 at 16:13

Boro · Accepted Answer · 2012-06-15T16:25:06.627

You had it almost all by yourself there were few issues though.

You should use getSelectionStart() rather than getCaretPosition().
Highlight should start from index not from index-1.

Please see the example below. Select what you want to highlight right click on the textArea or press the button to highlight your selection:

public class HighlightingTextArea {    
    public static void main(String[] args) {    
        SwingUtilities.invokeLater(new Runnable() {    
            @Override
            public void run() {
                final JTextArea textArea = new JTextArea(10, 44);
                textArea.append("AAAA\nBBBB\nAAAA\nCCCC\nDDDD\nAAAA");
                JButton b = new JButton(new AbstractAction("highlight") {    
                    @Override
                    public void actionPerformed(ActionEvent e) {
                        highlightTextAreaSelection(textArea);
                    }
                });
                textArea.addMouseListener(new MouseAdapter() {    
                    @Override
                    public void mousePressed(MouseEvent e) {
                        super.mousePressed(e);
                        if (e.getButton() == MouseEvent.BUTTON3) {
                            highlightTextAreaSelection(textArea);
                        }
                    }
                });
                JPanel panel = new JPanel(new BorderLayout());
                panel.add(textArea);
                panel.add(b, BorderLayout.SOUTH);
                JFrame f = new JFrame();
                f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                f.setContentPane(panel);
                f.pack();
                f.setVisible(true);
            }
        });
    }

    private static void highlightTextAreaSelection(JTextArea textArea) {
        String highlightedText = textArea.getSelectedText();
        if (highlightedText != null) {
            try {
                int index = textArea.getText().indexOf(highlightedText, textArea.getSelectionStart());
                textArea.getHighlighter().addHighlight(index, index + highlightedText.length(),
                        new DefaultHighlighter.DefaultHighlightPainter(Color.ORANGE));
            } catch (BadLocationException ex) {
            }
        }
    }
}

Great! This one helped me a lot! I don't know why I wrote index - 1 though :(....thanks a lot for your help!! — Sujay, Jun 15 '12 at 17:29

Highlight Text In JTextArea In Presence of Duplicate Lines

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