Java Swing How to - Style JTextPane with HTML CSS and StyleSheet

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Question

We would like to know how to style JTextPane with HTML CSS and StyleSheet.

Answer

//w  w  w  . ja v  a  2s.c  o m
import java.awt.BorderLayout;
import java.awt.Container;

import javax.swing.JFrame;
import javax.swing.JTextPane;
import javax.swing.text.Element;
import javax.swing.text.html.HTMLDocument;
import javax.swing.text.html.HTMLEditorKit;
import javax.swing.text.html.StyleSheet;

public class Main extends JFrame {

  StyleSheet styleSheet = new StyleSheet();
  HTMLDocument htmlDocument;
  HTMLEditorKit htmlEditorKit = new HTMLEditorKit();
  Element bodyElement;

  public static void main(String[] args) throws Exception {
    Main jTextPaneApp = new Main();
    jTextPaneApp.setVisible(true);
    Thread.currentThread().sleep(1000);
    jTextPaneApp.change();
  }

  public Main() {
    setSize(400, 400);   
    styleSheet.addRule(".someclass1 {color: blue;}");
    styleSheet.addRule(".someclass2 {color: green;}");

    htmlEditorKit.setStyleSheet(styleSheet);
    htmlDocument = (HTMLDocument) htmlEditorKit.createDefaultDocument();
    JTextPane jTextPane = new JTextPane();
    jTextPane.setEditorKit(htmlEditorKit);
    jTextPane.setDocument(htmlDocument);

    try {
      Element htmlElement = htmlDocument.getRootElements()[0];
      bodyElement = htmlElement.getElement(0);

      Container contentPane = getContentPane();
      contentPane.add(jTextPane, BorderLayout.CENTER);
      super.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

      addContent("<span class=someclass1>test 1</span><br>");
      addContent("<span class=someclass2>test 2</span><br>");

    } catch (Exception e) {
      e.printStackTrace();
    }
  }

  public void reapplyStyles() {
    Element sectionElem = bodyElement
        .getElement(bodyElement.getElementCount() - 1);
    int paraCount = sectionElem.getElementCount();
    for (int i = 0; i < paraCount; i++) {
      Element e = sectionElem.getElement(i);
      int rangeStart = e.getStartOffset();
      int rangeEnd = e.getEndOffset();
      htmlDocument.setParagraphAttributes(rangeStart, rangeEnd - rangeStart,
          e.getAttributes(), true);
    }
  }

  public void change() throws Exception {
    styleSheet = htmlEditorKit.getStyleSheet();
    styleSheet.addRule(".someclass1 {color: red;}");
    reapplyStyles();
    addContent("<span class=someclass1>test 3</span><br>");
  }

  private void addContent(String content) throws Exception {
    Element contentElement = bodyElement.getElement(bodyElement
        .getElementCount() - 1);

    StringBuffer sbHtml = new StringBuffer();
    sbHtml.append("<span class=someclass>" + content + "</span><br>");

    htmlDocument.insertBeforeEnd(contentElement, sbHtml.toString());
  }
}

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