Kleines (stark vereinfachtes) Beispiel zu Drag n Drop beim JTree

/**
 * 
 */
package de.tutorials;

import java.awt.Dimension;
import java.awt.Point;
import java.awt.dnd.DropTarget;
import java.awt.dnd.DropTargetAdapter;
import java.awt.dnd.DropTargetDropEvent;

import javax.swing.DropMode;
import javax.swing.JFrame;
import javax.swing.JScrollPane;
import javax.swing.JTree;
import javax.swing.TransferHandler;
import javax.swing.tree.DefaultMutableTreeNode;
import javax.swing.tree.TreePath;
import javax.swing.tree.TreeSelectionModel;

/**
 * @author Tom
 */
public class JTreeDragNDropExample extends JFrame {

	JTree tree;

	public JTreeDragNDropExample() {
		super("JTreeDragNDropExample");
		setDefaultCloseOperation(EXIT_ON_CLOSE);

		tree = new JTree();

		tree.setDragEnabled(true);
		tree.getSelectionModel().setSelectionMode(
				TreeSelectionModel.SINGLE_TREE_SELECTION);
		tree.setDropMode(DropMode.USE_SELECTION);
		tree.setDropTarget(new DropTarget(tree, TransferHandler.MOVE,
				new DropTargetAdapter() {
					@Override
					public void drop(DropTargetDropEvent dtde) {

						TreePath selectionPath = tree.getSelectionPath();
						TreePath sourcePath = selectionPath.getParentPath();

						DefaultMutableTreeNode selectedNode = (DefaultMutableTreeNode) selectionPath
								.getLastPathComponent();

						Point dropLocation = dtde.getLocation();
						TreePath targetPath = tree.getClosestPathForLocation(
								dropLocation.x, dropLocation.y);

						System.out.println("###################");

						System.out.println("srcPath: " + sourcePath);
						System.out.println("targetPath: " + targetPath);
						System.out.println("selectedNode: " + selectedNode);

						if (isDropAllowed(sourcePath, targetPath, selectedNode)) {
							System.out.println("drop accept");
							DefaultMutableTreeNode targetParentNode = (DefaultMutableTreeNode) targetPath
									.getLastPathComponent();
							DefaultMutableTreeNode sourceParentNode = (DefaultMutableTreeNode) sourcePath
									.getLastPathComponent();

							sourceParentNode.remove(selectedNode);
							targetParentNode.add(selectedNode);

							dtde.dropComplete(true);
							tree.updateUI();
						} else {
							System.out.println("drop: reject");
							dtde.rejectDrop();
							dtde.dropComplete(false);
						}
					}

					private boolean isDropAllowed(TreePath sourcePath,
							TreePath targetPath,
							DefaultMutableTreeNode selectedNode) {
						if (((DefaultMutableTreeNode) sourcePath
								.getLastPathComponent()).isLeaf()) {
						} else if (targetPath.equals(sourcePath)) {
							return false;
						}
						return selectedNode.isLeaf();
					}

				}));

		for (int currentRowIndex = 0; currentRowIndex < tree.getRowCount(); currentRowIndex++) {
			tree.expandRow(currentRowIndex);
		}

		JScrollPane scrollPane = new JScrollPane(tree);
		scrollPane.setPreferredSize(new Dimension(400, 100));

		add(scrollPane);

		pack();
		setVisible(true);

	}

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		new JTreeDragNDropExample();
	}
}