java-右键单击可以获得根节点，但其他节点为null

Question

我正在用Java创建文件浏览器，当我右键单击树中的节点（文件或文件夹名称）时，将弹出一个窗口，显示文件或文件夹信息。但是，当我使用鼠标右键单击时，只有应用程序只能识别根节点，而对于其他节点，它将显示null。而且我有一个walk（）方法可以遍历每个文件和文件夹，它运行良好，所以我不认为是因为这种方法。

public class NewJFrame extends javax.swing.JFrame {

private DefaultTreeModel model;
private JPopupMenu menu;

public NewJFrame() {
    initComponents();
    menu = new JPopupMenu();

    JMenuItem cut = new JMenuItem("Rename");  
    JMenuItem copy = new JMenuItem("Copy");
    JMenuItem paste = new JMenuItem("Paste");

    jTree1.addMouseListener(new MouseAdapter() {
        public void mouseClicked(MouseEvent e) {
            if (SwingUtilities.isRightMouseButton(e)) {

                menu.show(e.getComponent(), e.getX(), e.getY());

                int selRow = jTree1.getRowForLocation(e.getX(), e.getY());
                TreePath selPath = jTree1.getPathForLocation(e.getX(), e.getY());
                jTree1.setSelectionPath(selPath);
                    if (selRow > -1) {
                        jTree1.setSelectionRow(selRow);
                }
                System.out.println(jTree1.getClosestPathForLocation(
                                                 e.getX(), e.getY()));
                System.out.println("Path:  " + selPath);

            } else {
                menu.setVisible(false);
            }
        }
    });

    DefaultMutableTreeNode root = new DefaultMutableTreeNode("File 
                                                            System");
    model = new DefaultTreeModel(root);

    jTree1.setModel(model);
    jTree1 = new JTree(root);
    DefaultMutableTreeNode d = new DefaultMutableTreeNode("D:");
    root.add(d);
    walk("D:\\", d);

    jTree1.updateUI();
    }


    public void walk(String path, DefaultMutableTreeNode top) {

        File root = new File(path);

        File[] list = root.listFiles();
        if (list != null) {
            for (File f : list) {
                if (f.isDirectory()) {
                    DefaultMutableTreeNode node = new 
                                 DefaultMutableTreeNode(f.getName());
                    top.add(node);
                    walk(f.getAbsolutePath(), node);

                 } else {
                      DefaultMutableTreeNode node = new 
                              DefaultMutableTreeNode(f.getName());
                    top.add(node);

                }
           }   
        }
   }


 }