How to modify object assigned to JTree?

Question

Here is my NodeType class . Whenever i create a new jtree node , i create an instance of NodeType

public class NodeType {

    private String nodeType ;

    public NodeType (String nodeType ) {
        this.nodeType = nodeType ;
    }

    public String getNodeType() {
        return this.nodeType ;
    }
    public void setNodeType (String nodeType)   {
        this.nodeType = nodeType   ;
    }

}

I want to save the modified object associated with the node

btnSave = new JButton("Save");
    btnSave.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent e) { 
             DefaultMutableTreeNode node = (DefaultMutableTreeNode)
                     DynamicTree.tree.getLastSelectedPathComponent();

      String txt = desc.getTxt()  ;
  Object nodeInfo = node.getUserObject();
  if (node.isLeaf()) {
     ((NodeType) nodeInfo).setNodeType(txt  );     

DefaultTreeModel model = (DefaultTreeModel) DynamicTree.tree.getModel(); model.nodeChanged(node) ;
} } });

However the above "save " button does not work

Answer 1

I stole the example from How to use trees and modified it to allow me to change the node's user object

The primary update is done in the change button...

JButton change = new JButton("Change");
change.addActionListener(new ActionListener() {
    @Override
    public void actionPerformed(ActionEvent e) {
        DefaultMutableTreeNode node = (DefaultMutableTreeNode) tree.getLastSelectedPathComponent();

        if (node == null) {
            return;
        }

        Object nodeInfo = node.getUserObject();
        if (node.isLeaf()) {
            BookInfo book = (BookInfo) nodeInfo;
            book.bookName = "New Name";
            ((DefaultTreeModel)tree.getModel()).nodeChanged(node);
        }
        if (DEBUG) {
            System.out.println(nodeInfo.toString());
        }
    }
});

So, as you can see, I change the book.bookName, which is the node's user object and simply call ((DefaultTreeModel)tree.getModel()).nodeChanged(node); to update the view...

import java.awt.BorderLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.UIManager;

import javax.swing.JTree;
import javax.swing.tree.DefaultMutableTreeNode;
import javax.swing.tree.TreeSelectionModel;
import javax.swing.event.TreeSelectionEvent;
import javax.swing.event.TreeSelectionListener;

import java.net.URL;
import javax.swing.JButton;
import javax.swing.tree.DefaultTreeModel;

public class TreeDemo extends JPanel {

    private JTree tree;
    private static boolean DEBUG = false;

    //Optionally play with line styles.  Possible values are
    //"Angled" (the default), "Horizontal", and "None".
    private static boolean playWithLineStyle = false;
    private static String lineStyle = "Horizontal";

    //Optionally set the look and feel.
    private static boolean useSystemLookAndFeel = false;

    public TreeDemo() {
        super(new BorderLayout());

        //Create the nodes.
        DefaultMutableTreeNode top
                = new DefaultMutableTreeNode("The Java Series");
        createNodes(top);

        //Create a tree that allows one selection at a time.
        tree = new JTree();
        tree.setModel(new DefaultTreeModel(top));
        tree.getSelectionModel().setSelectionMode(TreeSelectionModel.SINGLE_TREE_SELECTION);

        if (playWithLineStyle) {
            System.out.println("line style = " + lineStyle);
            tree.putClientProperty("JTree.lineStyle", lineStyle);
        }

        //Create the scroll pane and add the tree to it. 
        JScrollPane treeView = new JScrollPane(tree);

        add(treeView);

        JButton change = new JButton("Change");
        change.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                DefaultMutableTreeNode node = (DefaultMutableTreeNode) tree.getLastSelectedPathComponent();

                if (node == null) {
                    return;
                }

                Object nodeInfo = node.getUserObject();
                if (node.isLeaf()) {
                    BookInfo book = (BookInfo) nodeInfo;
                    book.bookName = "New Name";
                    ((DefaultTreeModel)tree.getModel()).nodeChanged(node);
                }
                if (DEBUG) {
                    System.out.println(nodeInfo.toString());
                }
            }
        });
        add(change, BorderLayout.SOUTH);
    }

    private class BookInfo {

        public String bookName;

        public BookInfo(String book) {
            bookName = book;
        }

        public String toString() {
            return bookName;
        }
    }

    private void createNodes(DefaultMutableTreeNode top) {
        DefaultMutableTreeNode category = null;
        DefaultMutableTreeNode book = null;

        category = new DefaultMutableTreeNode("Books for Java Programmers");
        top.add(category);

        //original Tutorial
        book = new DefaultMutableTreeNode(new BookInfo("The Java Tutorial: A Short Course on the Basics"));
        category.add(book);

        //Tutorial Continued
        book = new DefaultMutableTreeNode(new BookInfo("The Java Tutorial Continued: The Rest of the JDK"));
        category.add(book);

        //JFC Swing Tutorial
        book = new DefaultMutableTreeNode(new BookInfo("The JFC Swing Tutorial: A Guide to Constructing GUIs"));
        category.add(book);

        //Bloch
        book = new DefaultMutableTreeNode(new BookInfo("Effective Java Programming Language Guide"));
        category.add(book);

        //Arnold/Gosling
        book = new DefaultMutableTreeNode(new BookInfo("The Java Programming Language"));
        category.add(book);

        //Chan
        book = new DefaultMutableTreeNode(new BookInfo("The Java Developers Almanac"));
        category.add(book);

        category = new DefaultMutableTreeNode("Books for Java Implementers");
        top.add(category);

        //VM
        book = new DefaultMutableTreeNode(new BookInfo("The Java Virtual Machine Specification"));
        category.add(book);

        //Language Spec
        book = new DefaultMutableTreeNode(new BookInfo("The Java Language Specification"));
        category.add(book);
    }

    /**
     * Create the GUI and show it. For thread safety, this method should be
     * invoked from the event dispatch thread.
     */
    private static void createAndShowGUI() {
        if (useSystemLookAndFeel) {
            try {
                UIManager.setLookAndFeel(
                        UIManager.getSystemLookAndFeelClassName());
            } catch (Exception e) {
                System.err.println("Couldn't use system look and feel.");
            }
        }

        //Create and set up the window.
        JFrame frame = new JFrame("TreeDemo");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        //Add content to the window.
        frame.add(new TreeDemo());

        //Display the window.
        frame.pack();
        frame.setLocationByPlatform(true);
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        //Schedule a job for the event dispatch thread:
        //creating and showing this application's GUI.
        javax.swing.SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                createAndShowGUI();
            }
        });
    }
}