Automatically update JTree node selection based on scroll position to indicate which link is currently active in the viewport of JEditorPane

• download example.jar
• download src.zip
• repository

Code

JScrollPane scroll = new JScrollPane(editor);
scroll.getVerticalScrollBar().getModel().addChangeListener(e -> {
  HTMLDocument.Iterator itr = doc.getIterator(HTML.Tag.A);
  for (; itr.isValid(); itr.next()) {
    try {
      Rectangle r = editor.modelToView(itr.getStartOffset());
      if (r != null && editor.getVisibleRect().contains(r.getLocation())) {
        searchTreeNode(tree, itr.getAttributes().getAttribute(HTML.Attribute.NAME));
        break;
      }
    } catch (BadLocationException ex) {
      UIManager.getLookAndFeel().provideErrorFeedback(editor);
    }
  }
});
// ...
tree.addTreeSelectionListener(e -> {
  if (!tree.isEnabled()) { // Ignore node selection from JEditorPane side
    return;
  }
  Object o = e.getNewLeadSelectionPath().getLastPathComponent();
  if (o instanceof DefaultMutableTreeNode) {
    DefaultMutableTreeNode node = (DefaultMutableTreeNode) o;
    String ref = Objects.toString(node.getUserObject());
    editor.scrollToReference(ref);
  }
});
// ...
private static void searchTreeNode(JTree tree, Object name) {
  TreeModel model = tree.getModel();
  DefaultMutableTreeNode root = (DefaultMutableTreeNode) model.getRoot();
  Collections.list((Enumeration<?>) root.preorderEnumeration()).stream()
      .filter(DefaultMutableTreeNode.class::isInstance)
      .map(DefaultMutableTreeNode.class::cast)
      .filter(node -> Objects.equals(name, Objects.toString(node.getUserObject())))
      .findFirst()
      .ifPresent(node -> {
        tree.setEnabled(false); // Disable TreeSelectionListener in JTree
        TreePath path = new TreePath(node.getPath());
        tree.setSelectionPath(path);
        tree.scrollPathToVisible(path);
        tree.setEnabled(true); // Restores TreeSelectionListener in JTree
      });
}

References

• Automatically update JTree node selection based on scroll position to indicate which link is currently active in the viewport of JEditorPane(Japanese)