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Task 1

import javax.swing.tree.*;

Next, create a set of DefaultMutableTreeNode objects in the TreeExample constructor, one for each node in the class hierarchy:

Component
  Container
    Box
    JComponent
      AbstractButton
        JButton
        JMenuItem
        JToggleButton
      JLabel
      ...  [literally "..."]

Use constructs such as:

DefaultMutableTreeNode component = 
  new DefaultMutableTreeNode("Component");

DefaultMutableTreeNode component = 
  new DefaultMutableTreeNode("Component");
DefaultMutableTreeNode container = 
  new DefaultMutableTreeNode("Container");
DefaultMutableTreeNode box = 
  new DefaultMutableTreeNode("Box");
DefaultMutableTreeNode jComponent = 
  new DefaultMutableTreeNode("JComponent");
DefaultMutableTreeNode abstractButton = 
  new DefaultMutableTreeNode("AbstractButton");
DefaultMutableTreeNode jButton = 
  new DefaultMutableTreeNode("JButton");
DefaultMutableTreeNode jMenuItem = 
  new DefaultMutableTreeNode("JMenuItem");
DefaultMutableTreeNode jToggle = 
  new DefaultMutableTreeNode("JToggleButton");
DefaultMutableTreeNode jLabel = 
  new DefaultMutableTreeNode("JLabel");
DefaultMutableTreeNode etc = 
  new DefaultMutableTreeNode("...");

Once you've created all the nodes, add them to each other to construct the hierarchy. DefaultMutableTreeNode contains an add method that defines the children of a node.

component.add(container);
container.add(box);
container.add(jComponent);
jComponent.add(abstractButton);
abstractButton.add(jButton);
abstractButton.add(jMenuItem);
abstractButton.add(jToggle);
jComponent.add(jLabel);
jComponent.add(etc);

Once you have the hierarchy setup, create a class that implements TreeSelectionListener. Have it print the label of the selected cell and the full path to the cell.

Import the javax.swing.event package.

Define the class similar to the following:

class MyTreeSelectionListener 
    implements TreeSelectionListener {
  public void valueChanged (
              TreeSelectionEvent event) {
    TreePath path = event.getPath();
    System.out.println ("Selected: " + 
      path.getLastPathComponent());
    Object elements[] = path.getPath();
    for (int i=0; i<elements.length; i++) {
      System.out.print ("->" + elements[i]);
    }
    System.out.println ();
  }
}

Once you've defined a TreeSelectionListener class, create an instance of it.

TreeSelectionListener listener = 
  new MyTreeSelectionListener();

Create a TreePanel and pass it the root of your component hierarchy tree and the TreeSelectionListener. Add the panel to the frame. You'll finish up the TreePanel description next.

TreePanel tp = new TreePanel(component, listener);
Container content = getContentPane();
content.add(tp, BorderLayout.CENTER);

The TreePanel class will offer the visual representation of the tree. Modify the constructor of TreePanel so that it creates a JTree called tree attached to the root passed in to the constructor.

JTree tree = new JTree(root);

Change the lineStyle client property of the tree to Angled.

tree.putClientProperty("JTree.lineStyle", "Angled");

Associate the TreeSelectionListener to the JTree if it is non-null.

if (listener != null)
  tree.addTreeSelectionListener (listener);

Then, create a JScrollPane object, and place the tree in it.

JScrollPane sp = new JScrollPane(tree);

Save everything and compile the program. Then run it to see the results.

javac TreeExample.java
java TreeExample

The dependency checker automatically determines that TreePanel.java needs to be compiled.

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