treeexpansiondemo.java

《java事件处理指南》一书的代码,好东西

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

public class TreeExpansionDemo extends JFrame 
                             implements TreeWillExpandListener
{
   private JTree tree;
   private JCheckBox jcb;
   private JTextField jtf;

   public TreeExpansionDemo() 
   {
/*  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 TreeWillExpandListener.   The                 */
/*  TreeExpansionDemo class serves as the TreeWillExpandListener, so    */
/*  the "this" reference is passed to the addTreeWillExpandListener()   */
/*  method.                                                             */

      tree = new JTree(dtm);
      tree.setShowsRootHandles(true);
      tree.addTreeWillExpandListener(this);

      jcb = new JCheckBox("permission");
      jcb.setBorder(BorderFactory.createLineBorder(Color.black));
      jcb.setBorderPainted(true);
      jcb.setPreferredSize(new Dimension(100, 30));

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

      JPanel panel = new JPanel();
      panel.add(jcb);
      panel.add(jtf);

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

      setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      setBounds(100, 100, 400, 300);
      setVisible(true);
   }

/*  The TreeExpansionDemo class provides implementation of the     */
/*  treeWillExpand() method.  The method checks to see if the      */
/*  "permission" checkbox is checked.  If it is, the expansion     */
/*  is allowed to proceed.  If the checkbox is not checked, an     */
/*  ExpandVetoException is thrown and the expansion is canceled.   */
/*  The treeWillCollapse() method is not used in this example so   */
/*  it is implemented as a stub method.                            */

   public void treeWillExpand(TreeExpansionEvent event)
                                  throws ExpandVetoException 
   {
      if ( jcb.isSelected() )
      {
         TreePath path = event.getPath();
         jtf.setText(""+path.getLastPathComponent()+" node expanded");
      }
      else
      {
         jtf.setText("permission denied");
         throw new ExpandVetoException(event);
      }

   }

   public void treeWillCollapse(TreeExpansionEvent event)
                              throws ExpandVetoException {}

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