TreeEditor: Customizing Drag and Drop

JTree is a Java GUI component for tree structure.  The tree structure is represented by nodes (DefaultMutableTreeNode).  The path or the placement of the node in the tree is represented by TreePath.

DefaultMutableTreeNode selectedNode = (DefaultMutableTreeNode) tree.getLastSelectedPathComponent();

Use TransferHandler for drag and drop.  Supposing a class derived from TransferHandler called MenuTransferHandler handles drag and drop, set the TransferHandler as follows:

        MenuTransferHandler handler = new MenuTransferHandler();
        treeEditor.tree.setTransferHandler(handler);

The copied new node should be generated at TransferHandler#createTransferable().  Here shows the function copy() that may come in handy in writing createTransferable().  copy() should be called recursively.

    private DefaultMutableTreeNode copy(TreeNode node) {
        DefaultMutableTreeNode newNode = new DefaultMutableTreeNode(node);
        if (!node.isLeaf()) {
            @SuppressWarnings("unchecked")
            Enumeration<TreeNode> list = node.children();
            while (list.hasMoreElements()) {
                TreeNode n = list.nextElement();
                newNode.add(copy(n));
            }
        }
        return newNode;
    }

javamenu is a program that uses TreeEditor for editing menu tree structure.