treeexpansiondemo2.java

来自「《java事件处理指南》一书的代码,好东西」· Java 代码 · 共 94 行

import javax.swing.*;
import javax.swing.tree.*;
import javax.swing.event.*;
import java.awt.*;
import java.awt.event.*;

public class TreeExpansionDemo2 extends JFrame  
{
   private JTree tree;
   private JTextField jtf;

   public TreeExpansionDemo2() 
   {
/*  A Collection of DefaultMutableTreeNode objects are created that  */
/*  will form the components of a tree.                              */

      DefaultMutableTreeNode league = 
               new DefaultMutableTreeNode("Soccer League");

      DefaultMutableTreeNode north = 
                  new DefaultMutableTreeNode("North Division");
      DefaultMutableTreeNode south = 
                  new DefaultMutableTreeNode("South Divison");

      DefaultMutableTreeNode jets = 
                      new DefaultMutableTreeNode("Jets");
      DefaultMutableTreeNode raiders = 
                      new DefaultMutableTreeNode("Raiders");
      DefaultMutableTreeNode fins = 
                      new DefaultMutableTreeNode("Fins");
      DefaultMutableTreeNode shooters = 
                      new DefaultMutableTreeNode("Shooters");
      DefaultMutableTreeNode lions = 
                      new DefaultMutableTreeNode("Lions");
      DefaultMutableTreeNode tigers = 
                      new DefaultMutableTreeNode("Tigers");

/*  The node hierarchy is loaded into a DefaultTreeModel object.   */

      DefaultTreeModel dtm = new DefaultTreeModel(league);
      dtm.insertNodeInto(north, league, 0);
      dtm.insertNodeInto(south, league, 1);
      dtm.insertNodeInto(jets, north, 0);
      dtm.insertNodeInto(raiders, north, 1);
      dtm.insertNodeInto(fins, north, 2);
      dtm.insertNodeInto(shooters, south, 0);
      dtm.insertNodeInto(lions, south, 1);
      dtm.insertNodeInto(tigers, south, 2);

/*  A JTree object is created using the previously created tree model.  */
/*  The JTree registers a TreeExpansionListener.                        */

      tree = new JTree(dtm);
      tree.setShowsRootHandles(true);
      tree.addTreeExpansionListener(new TreeExpansionHandler());

      jtf = new JTextField(20);
      jtf.setEditable(false);

      getContentPane().add( new JScrollPane(tree), BorderLayout.CENTER );
      getContentPane().add( jtf, BorderLayout.SOUTH );

      setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      setBounds(100, 100, 300, 300);
      setVisible(true);
   }

/*   The TreeExpansionListener is implemented as an inner class.      */
/*   When the user expands or collapses a node, a TreeExpansionEvent  */
/*   is generated and sent to either the treeCollapsed() or           */
/*   treeExpanded() methods.  The identity of the node that caused    */
/*   the event is listed in a JTextField.                             */

   class TreeExpansionHandler implements TreeExpansionListener
   {
      public void treeCollapsed(TreeExpansionEvent event)
      {
         TreePath path = event.getPath();
         jtf.setText(""+path.getLastPathComponent()+" node collapsed");
      }

      public void treeExpanded(TreeExpansionEvent event)
      {
         TreePath path = event.getPath();
         jtf.setText(""+path.getLastPathComponent()+" node expanded");
      }
   }

   public static void main(String args[]) 
   {
      TreeExpansionDemo2 demo = new TreeExpansionDemo2();
   }
}