Highlight current row in JTextPane

Question

I\'m trying for more than 2 days to implement a specific requirement for a text editor window... unfortunately without success so far :(

The goal is to get a text editor

Answer 1

Below is the code to extract text from current line. You can use same logic to get required indexes and highlight text

    private String getCurrentEditLine() {
        int readBackChars = 100;
        int caretPosition = scriptEditor.getCaretPosition();

        if (caretPosition == 0) {
            return null;
        }

        StyledDocument doc = scriptEditor.getStyledDocument();

        int offset = caretPosition <= readBackChars ? 0 : caretPosition
                - readBackChars;

        String text = null;
        try {
            text = doc.getText(offset, caretPosition);
        } catch (BadLocationException e) {
        }

        if (text != null) {
            int idx = text.lastIndexOf("\n");
            if(idx != -1) {
                return text.substring(idx);
            }else {
                return text;
            }
        }

        return null;
    }

Answer 2

I think this might be difficult to achieve using highlighters - I don't think it is what they were designed for. You may need to do it with custom painting code:

import java.awt.Color;
import java.awt.Graphics;
import java.awt.Rectangle;

import javax.swing.JFrame;
import javax.swing.JTextPane;
import javax.swing.text.BadLocationException;

public class HighlightLineTest {
    private static class HighlightLineTextPane extends JTextPane {
        public HighlightLineTextPane() {
            // Has to be marked as transparent so the background is not replaced by 
            // super.paintComponent(g);
            setOpaque(false);
        }

        @Override
        protected void paintComponent(Graphics g) {
            g.setColor(getBackground());
            g.fillRect(0, 0, getWidth(), getHeight());
            try {
                Rectangle rect = modelToView(getCaretPosition());
                if (rect != null) {
                    g.setColor(Color.CYAN);
                    g.fillRect(0, rect.y, getWidth(), rect.height);
                }
            } catch (BadLocationException e) {
            }
            super.paintComponent(g);
        }

        @Override
        public void repaint(long tm, int x, int y, int width, int height) {
            // This forces repaints to repaint the entire TextPane.
            super.repaint(tm, 0, 0, getWidth(), getHeight());
        }
    }

    public static void main(String[] args) {
        JFrame frame = new JFrame("Highlight test");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.add(new HighlightLineTextPane());
        frame.setBounds(100, 100, 300, 400);
        frame.setVisible(true);
    }
}

Answer 3

http://tips4java.wordpress.com/2008/10/29/line-painter/

I think this is what you are looking for. I took that LinePainter class and copied your constructor over into a main method, took out your highlighter parts and added a new LinePainter(textPane); Works like a charm