implements TreeModel to create tree model : Tree Model « Swing JFC « Java

implements TreeModel to create tree model

implements TreeModel to create tree model
 * Copyright (c) 2000 David Flanagan.  All rights reserved.
 * This code is from the book Java Examples in a Nutshell, 2nd Edition.
 * It is provided AS-IS, WITHOUT ANY WARRANTY either expressed or implied.
 * You may study, use, and modify it for any non-commercial purpose.
 * You may distribute it non-commercially as long as you retain this notice.
 * For a commercial use license, or to purchase the book (recommended),
 * visit

import java.awt.BorderLayout;
import java.awt.Component;
import java.awt.Container;
import java.awt.Font;
import java.awt.Point;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;

import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JScrollPane;
import javax.swing.JTree;
import javax.swing.event.TreeModelListener;
import javax.swing.event.TreeSelectionEvent;
import javax.swing.event.TreeSelectionListener;
import javax.swing.tree.TreeCellRenderer;
import javax.swing.tree.TreeModel;
import javax.swing.tree.TreePath;
import javax.swing.tree.TreeSelectionModel;

 * This class is a JTree subclass that displays the tree of AWT or Swing
 * component that make up a GUI.
public class ComponentTree extends JTree {
   * All this constructor method has to do is set the TreeModel and
   * TreeCellRenderer objects for the tree. It is these classes (defined
   * below) that do all the real work.
  public ComponentTree(Component c) {
    super(new ComponentTreeModel(c));
    setCellRenderer(new ComponentCellRenderer(getCellRenderer()));

   * The TreeModel class puts hierarchical data in a form that the JTree can
   * display. This implementation interprets the containment hierarchy of a
   * Component for display by the ComponentTree class. Note that any kind of
   * Object can be a node in the tree, as long as the TreeModel knows how to
   * handle it.
  static class ComponentTreeModel implements TreeModel {
    Component root; // The root object of the tree

    // Constructor: just remember the root object
    public ComponentTreeModel(Component root) {
      this.root = root;

    // Return the root of the tree
    public Object getRoot() {
      return root;

    // Is this node a leaf? (Leaf nodes are displayed differently by JTree)
    // Any node that isn't a container is a leaf, since they cannot have
    // children. We also define containers with no children as leaves.
    public boolean isLeaf(Object node) {
      if (!(node instanceof Container))
        return true;
      Container c = (Container) node;
      return c.getComponentCount() == 0;

    // How many children does this node have?
    public int getChildCount(Object node) {
      if (node instanceof Container) {
        Container c = (Container) node;
        return c.getComponentCount();
      return 0;

    // Return the specified child of a parent node.
    public Object getChild(Object parent, int index) {
      if (parent instanceof Container) {
        Container c = (Container) parent;
        return c.getComponent(index);
      return null;

    // Return the index of the child node in the parent node
    public int getIndexOfChild(Object parent, Object child) {
      if (!(parent instanceof Container))
        return -1;
      Container c = (Container) parent;
      Component[] children = c.getComponents();
      if (children == null)
        return -1;
      for (int i = 0; i < children.length; i++) {
        if (children[i] == child)
          return i;
      return -1;

    // This method is only required for editable trees, so it is not
    // implemented here.
    public void valueForPathChanged(TreePath path, Object newvalue) {

    // This TreeModel never fires any events (since it is not editable)
    // so event listener registration methods are left unimplemented
    public void addTreeModelListener(TreeModelListener l) {

    public void removeTreeModelListener(TreeModelListener l) {

   * A TreeCellRenderer displays each node of a tree. The default renderer
   * displays arbitrary Object nodes by calling their toString() method. The
   * Component.toString() method returns long strings with extraneous
   * information. Therefore, we use this "wrapper" implementation of
   * TreeCellRenderer to convert nodes from Component objects to useful String
   * values before passing those String values on to the default renderer.
  static class ComponentCellRenderer implements TreeCellRenderer {
    TreeCellRenderer renderer; // The renderer we are a wrapper for

    // Constructor: just remember the renderer
    public ComponentCellRenderer(TreeCellRenderer renderer) {
      this.renderer = renderer;

    // This is the only TreeCellRenderer method.
    // Compute the string to display, and pass it to the wrapped renderer
    public Component getTreeCellRendererComponent(JTree tree, Object value,
        boolean selected, boolean expanded, boolean leaf, int row,
        boolean hasFocus) {
      String newvalue = value.getClass().getName(); // Component type
      String name = ((Component) value).getName(); // Component name
      if (name != null)
        newvalue += " (" + name + ")"; // unless null
      // Use the wrapped renderer object to do the real work
      return renderer.getTreeCellRendererComponent(tree, newvalue,
          selected, expanded, leaf, row, hasFocus);

   * This main() method demonstrates the use of the ComponentTree class: it
   * puts a ComponentTree component in a Frame, and uses the ComponentTree to
   * display its own GUI hierarchy. It also adds a TreeSelectionListener to
   * display additional information about each component as it is selected
  public static void main(String[] args) {
    // Create a frame for the demo, and handle window close requests
    JFrame frame = new JFrame("ComponentTree Demo");
    frame.addWindowListener(new WindowAdapter() {
      public void windowClosing(WindowEvent e) {

    // Create a scroll pane and a "message line" and add them to the
    // center and bottom of the frame.
    JScrollPane scrollpane = new JScrollPane();
    final JLabel msgline = new JLabel(" ");
    frame.getContentPane().add(scrollpane, BorderLayout.CENTER);
    frame.getContentPane().add(msgline, BorderLayout.SOUTH);

    // Now create the ComponentTree object, specifying the frame as the
    // component whose tree is to be displayed. Also set the tree's font.
    JTree tree = new ComponentTree(frame);
    tree.setFont(new Font("SansSerif", Font.BOLD, 12));

    // Only allow a single item in the tree to be selected at once

    // Add an event listener for notifications when
    // the tree selection state changes.
    tree.addTreeSelectionListener(new TreeSelectionListener() {
      public void valueChanged(TreeSelectionEvent e) {
        // Tree selections are referred to by "path"
        // We only care about the last node in the path
        TreePath path = e.getPath();
        Component c = (Component) path.getLastPathComponent();
        // Now we know what component was selected, so
        // display some information about it in the message line
        if (c.isShowing()) {
          Point p = c.getLocationOnScreen();
          msgline.setText("x: " + p.x + "  y: " + p.y + "  width: "
              + c.getWidth() + "  height: " + c.getHeight());
        } else {
          msgline.setText("component is not showing");

    // Now that we've set up the tree, add it to the scrollpane

    // Finally, set the size of the main window, and pop it up.
    frame.setSize(600, 400);


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