TreeModelListener没有响应它所订阅的TreeModel中的更改

Question

我有些理解为什么我无法让TreeModelChanged监听器响应它所订阅的模型中的更改。

我设法通过一个小例子重现了这个问题。

只要将新节点添加到树中，SysOut消息就不会打印到控制台。

我打算用一些命令替换SysOut消息来重绘树。目前我正在使用SysOut消息来证明听众没有被解雇。

我错过了一些基本的东西吗？

import java.awt.Dimension;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTree;
import javax.swing.event.TreeModelEvent;
import javax.swing.event.TreeModelListener;
import javax.swing.tree.DefaultMutableTreeNode;
import javax.swing.tree.DefaultTreeModel;


public class TreeTest {

    private JTree t;
    private DefaultTreeModel m ;

    public static void main(String[] args) {
         new TreeTest();

    }

    public TreeTest() {

        //Draw Frame & Panel  - set dimensions
        JFrame f = new JFrame();
        f.setSize(new Dimension(800,600));
        JPanel p = new JPanel();
        p.setSize(new Dimension(800,600));



        //Create a Tree Model. Give it a String at the root.
        m = new DefaultTreeModel(new DefaultMutableTreeNode("Root"));

        //Create a tree and add the Model to it
        t = new JTree();
        t.setModel(m);


        //Try a Tree Model Listener
        m.addTreeModelListener(new TreeModelListener() {

            private void doSomething() {
                //Should fire whenever a node is added to the model
                System.out.println("Responding to TreeModelListener");
            }
            @Override
            public void treeStructureChanged(TreeModelEvent e) {
                doSomething();

            }

            @Override
            public void treeNodesRemoved(TreeModelEvent e) {
                doSomething();

            }

            @Override
            public void treeNodesInserted(TreeModelEvent e) {
                doSomething();

            }

            @Override
            public void treeNodesChanged(TreeModelEvent e) {
                doSomething();

            }
        });     

        //Add listener to a button which adds nodes to the tree when clicked
        JButton addNode = new JButton("Add node");
        addNode.addActionListener(new ActionListener() {

            @Override
            public void actionPerformed(ActionEvent e) {
                DefaultMutableTreeNode newNode = new DefaultMutableTreeNode("New Node");
                DefaultMutableTreeNode root = (DefaultMutableTreeNode) m.getRoot();
                root.add(newNode);
            }
        });

        JScrollPane s = new JScrollPane(t);


        p.add(s);
        p.add(addNode);

        p.setVisible(true);
        f.add(p);
        f.setVisible(true);
    }

}