MainPanel.java

// -*- mode:java; encoding:utf-8 -*-
// vim:set fileencoding=utf-8:
// @homepage@

package example;

import java.awt.*;
import javax.swing.*;
import javax.swing.text.MutableAttributeSet;
import javax.swing.text.SimpleAttributeSet;
import javax.swing.text.StyleConstants;
import javax.swing.text.StyledDocument;

public final class MainPanel extends JPanel {
  private MainPanel() {
    super(new BorderLayout());
    JTextPane textPane = new JTextPane();
    textPane.setComponentPopupMenu(new HtmlColorPopupMenu());
    // textPane.setEditorKit(new HTMLEditorKit());
    textPane.setContentType("text/html");

    JTextArea textArea = new JTextArea();
    textArea.setText(textPane.getText());

    JTabbedPane tabbedPane = new JTabbedPane();
    tabbedPane.addTab("JTextPane", new JScrollPane(textPane));
    tabbedPane.addTab("JTextArea", new JScrollPane(textArea));
    tabbedPane.addChangeListener(e -> {
      JTabbedPane t = (JTabbedPane) e.getSource();
      boolean isHtmlMode = t.getSelectedIndex() == 0;
      if (isHtmlMode) {
        textPane.setText(textArea.getText());
        // textPane.setText("");
        // HTMLEditorKit hek = (HTMLEditorKit) textPane.getEditorKit();
        // HTMLDocument doc = (HTMLDocument) textPane.getStyledDocument();
        // hek.insertHTML(doc, 0, textArea.getText(), 0, 0, null);
      } else {
        String str = textPane.getText();
        textArea.setText(str);
        // // Removing HTML from a Java String - Stack Overflow
        // // https://stackoverflow.com/questions/240546/removing-html-from-a-java-string
        // // Test >>>>
        // ParserDelegator delegator = new ParserDelegator();
        // StringBuilder s = new StringBuilder();
        // delegator.parse(new StringReader(str), new HTMLEditorKit.ParserCallback() {
        //   @Override public void handleText(char[] text, int pos) {
        //     s.append(text);
        //   }
        // }, Boolean.TRUE);
        // System.out.println(s.toString());
        // // <<<<
      }
      t.revalidate();
    });
    add(tabbedPane);
    setPreferredSize(new Dimension(320, 240));
  }

  public static void main(String[] args) {
    EventQueue.invokeLater(MainPanel::createAndShowGui);
  }

  private static void createAndShowGui() {
    try {
      UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
    } catch (UnsupportedLookAndFeelException ignored) {
      Toolkit.getDefaultToolkit().beep();
    } catch (ClassNotFoundException | InstantiationException | IllegalAccessException ex) {
      ex.printStackTrace();
      return;
    }
    JFrame frame = new JFrame("@title@");
    frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
    frame.getContentPane().add(new MainPanel());
    frame.pack();
    frame.setLocationRelativeTo(null);
    frame.setVisible(true);
  }
}

final class HtmlColorPopupMenu extends JPopupMenu {
  /* default */ HtmlColorPopupMenu() {
    super();
    MutableAttributeSet red = new SimpleAttributeSet();
    StyleConstants.setForeground(red, Color.RED);
    MutableAttributeSet green = new SimpleAttributeSet();
    StyleConstants.setForeground(green, Color.GREEN);
    MutableAttributeSet blue = new SimpleAttributeSet();
    StyleConstants.setForeground(blue, Color.BLUE);

    add("Red").addActionListener(e -> {
      JTextPane t = (JTextPane) getInvoker();
      StyledDocument doc = t.getStyledDocument();
      int start = t.getSelectionStart();
      int end = t.getSelectionEnd();
      doc.setCharacterAttributes(start, end - start, red, false);
    });
    add("Green").addActionListener(e -> {
      JTextPane t = (JTextPane) getInvoker();
      StyledDocument doc = t.getStyledDocument();
      int start = t.getSelectionStart();
      int end = t.getSelectionEnd();
      doc.setCharacterAttributes(start, end - start, green, false);
    });
    add("Blue").addActionListener(e -> {
      JTextPane t = (JTextPane) getInvoker();
      StyledDocument doc = t.getStyledDocument();
      int start = t.getSelectionStart();
      int end = t.getSelectionEnd();
      doc.setCharacterAttributes(start, end - start, blue, false);
    });
  }

  @Override public void show(Component c, int x, int y) {
    if (c instanceof JTextPane) {
      JTextPane t = (JTextPane) c;
      int start = t.getSelectionStart();
      int end = t.getSelectionEnd();
      boolean flag = end - start > 0;
      for (MenuElement me : getSubElements()) {
        me.getComponent().setEnabled(flag);
      }
      super.show(c, x, y);
    }
  }
}