How can I set each character to a different color/background color in a JTextPane?

Question

I've been searching for this for a while and so far all I've been able to come up with is how to create a style and apply it to a character like so:

StyledDocument doc = (StyledDocument) new DefaultStyledDocument();
JTextPane textpane = new JTextPane(doc);
textpane.setText("Test");
javax.swing.text.Style style = textpane.addStyle("Red", null);
StyleConstants.setForeground(style, Color.RED);
doc.setCharacterAttributes(0, 1, textpane.getStyle("Red"), true); 

This is useful if you have only a few styles in your document and want to store them by name so that you can apply them easily later on. In my application I want to be able to set the foreground color (one of only a few values) and the background color (grayscale, many different values) independently for every character in the text. It seems like a huge waste to create potentially hundreds/thousands of different styles for this. Is there a way to set these attributes without having to create a new style each time? It would be much easier if I only had to render the text but I also need to make it editable as well. Is there a way to do this with JTextPane, or is there another swing class that offers this functionality?

Answer 1

If you want to change the style for each character in a textpane, here is a complete random way to do it. You create a different attribute set for each character. Up to you to find appropriate combination (foreground/background contrast, not too much difference in size of the chars, etc...). You could also store the different styles you have already applied so that you don't use the same one twice.

import java.awt.Color;
import java.util.Random;

import javax.swing.JFrame;
import javax.swing.JScrollPane;
import javax.swing.JTextPane;
import javax.swing.text.DefaultStyledDocument;
import javax.swing.text.SimpleAttributeSet;
import javax.swing.text.StyleConstants;
import javax.swing.text.StyledDocument;

public class TestDifferentStyles {
    private void initUI() {
        JFrame frame = new JFrame(TestDifferentStyles.class.getSimpleName());
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        StyledDocument doc = new DefaultStyledDocument();
        JTextPane textPane = new JTextPane(doc);
        textPane.setText("Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has "
                + "been the industry's standard dummy text ever since the 1500s, when an unknown printer took a galley of "
                + "type and scrambled it to make a type specimen book. It has survived not only five centuries, but also the "
                + "leap into electronic typesetting, remaining essentially unchanged. It was popularised in the 1960s with the"
                + " release of Letraset sheets containing Lorem Ipsum passages, and more recently with desktop publishing "
                + "software like Aldus PageMaker including versions of Lorem Ipsum.");

        Random random = new Random();
        for (int i = 0; i < textPane.getDocument().getLength(); i++) {
            SimpleAttributeSet set = new SimpleAttributeSet();
            // StyleConstants.setBackground(set, new Color(random.nextInt(256), random.nextInt(256), random.nextInt(256)));
            StyleConstants.setForeground(set, new Color(random.nextInt(256), random.nextInt(256), random.nextInt(256)));
            StyleConstants.setFontSize(set, random.nextInt(12) + 12);
            StyleConstants.setBold(set, random.nextBoolean());
            StyleConstants.setItalic(set, random.nextBoolean());
            StyleConstants.setUnderline(set, random.nextBoolean());

            doc.setCharacterAttributes(i, 1, set, true);
        }

        frame.add(new JScrollPane(textPane));
        frame.setSize(500, 400);
        frame.setVisible(true);
    }

    public static void main(String[] args) {

        javax.swing.SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                new TestDifferentStyles().initUI();
            }
        });
    }

}