Java Swing - 如何实现从一个JTree到另一个JTree的拖放...

import java.awt.BorderLayout;
import java.util.ArrayList;
import java.util.List;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTree;
import javax.swing.tree.DefaultMutableTreeNode;
import javax.swing.tree.DefaultTreeModel;
import javax.swing.tree.TreeNode;
import javax.swing.tree.TreePath;

public class Main extends JFrame {

  public Main() {
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    TreeNode root = getNodes();
    DefaultTreeModel model = new DefaultTreeModel(root);
    JTree tree = new JTree(model);
    tree.setRootVisible(false);

    JButton add = new JButton("add new");
    add.addActionListener(e->{
      DefaultMutableTreeNode selectedNode = (DefaultMutableTreeNode) tree
          .getLastSelectedPathComponent();
      if (selectedNode == null) {
        return;
      }
      MyObject obj = (MyObject) selectedNode.getUserObject();
      MyObject newChild = new MyObject(obj.name + "-"
          + (obj.childs.size() + 1));
      obj.childs.add(newChild);
      DefaultMutableTreeNode newNode = new DefaultMutableTreeNode(newChild);
      model.insertNodeInto(newNode, selectedNode,
          selectedNode.getChildCount());
      TreeNode[] nodes = model.getPathToRoot(newNode);
      TreePath path = new TreePath(nodes);
      tree.scrollPathToVisible(path);
    });

    JButton print = new JButton("print childs");
    print.addActionListener(e-> {
      DefaultMutableTreeNode selectedNode = (DefaultMutableTreeNode) tree
          .getLastSelectedPathComponent();
      if (selectedNode == null) {
        return;
      }
      MyObject obj = (MyObject) selectedNode.getUserObject();
      System.out.println(obj.childs);
    });
    JPanel btns = new JPanel();
    btns.add(add);
    btns.add(print);

    add(new JScrollPane(tree));
    add(btns, BorderLayout.SOUTH);
    pack();
    setVisible(true);
  }
  private TreeNode getNodes() {
    MyObject obj1 = new MyObject("1");
    MyObject obj2 = new MyObject("1-1");

    obj1.childs.add(obj2);
    obj2.childs.add(new MyObject("2-1"));
    obj2.childs.add(new MyObject("2-2"));

    obj1.childs.add(new MyObject("1-2"));
    obj1.childs.add(new MyObject("1-3"));

    DefaultMutableTreeNode root = new DefaultMutableTreeNode();
    construct(obj1, root);
    return root;
  }
  private void construct(MyObject obj1, DefaultMutableTreeNode root) {
    DefaultMutableTreeNode node = new DefaultMutableTreeNode(obj1);
    root.add(node);
    for (MyObject o : obj1.childs) {
      construct(o, node);
    }
  }
  public static void main(String... strings) {
    new Main();
  }
}

class MyObject {
  public String name;
  public List<MyObject> childs = new ArrayList<>();

  public MyObject(String name) {
    this.name = name;
  }
  @Override
  public String toString() {
    return name;
  }
}