restorabletree.java

一款即时通讯软件

/**
 * RestorableTree.java
 *
 * (C) Copyright Knowledge Media Institute 2000-2002
 *
 *
 * Created: Mon Jan 14 16:12:41 2002
 *
 * $Id: RestorableTree.java,v 1.1 2007/05/01 10:51:31 chris Exp $
 */

package edu.ou.kmi.util;

import java.util.*;

import javax.swing.*;
import javax.swing.tree.*;

/**
 * Tree with a restorable state.
 *
 * By "state" I mean expansion state of each node.
 * State of the tree is saved calling method {@link #saveState()} and restored by {@link #restoreState()}.
 * This class is abstract, user has to redefine method nodesAreEqual().
 *
 * @author "Matt Koss" <[e-mail]>
 * @version 1.0
 */
public abstract class RestorableTree extends JTree {

  Enumeration expandedNodes;
  protected DefaultMutableTreeNode nodeRoot;

  public RestorableTree( TreeModel model ) {
    super( model );

    nodeRoot = (DefaultMutableTreeNode) getModel().getRoot();
  }

  /**
   * Saves the state of the tree.
   *
   */
  public void saveState() {
    expandedNodes = getExpandedDescendants( new TreePath( nodeRoot ) );
  }

  /**
   * Tries to restore a state of each node.
   * If node does not exist, it is skipped.
   *
   */
  public void restoreState() {
    if ( expandedNodes != null && nodeRoot.getChildCount() != 0 ) {
      while ( expandedNodes.hasMoreElements() ) {
	TreePath path = (TreePath) expandedNodes.nextElement();
	Object[] o = path.getPath();
	DefaultMutableTreeNode node = (DefaultMutableTreeNode) nodeRoot.getFirstChild();

	for ( int i = 1; i < o.length; i++ ) { // skip the first node
	  // go through all the nodes in the path and try to expand them

	  // find the relevant frame
	  while ( node != null ) {
	    if ( nodesAreEqual( (DefaultMutableTreeNode)o[i], node ) ) {
	      TreePath newPath = new TreePath( node.getPath() );
	      // expand found node, if it is not already
	      if ( ! isExpanded( newPath ) ) {
		expandPath( newPath );
	      }
	      if ( node.getChildCount() != 0 ) {
		node = (DefaultMutableTreeNode) node.getFirstChild();
	      } else {
		node = null;
	      }
	      break;
	    } else {
	      node = (DefaultMutableTreeNode) node.getNextSibling();
	    }
	  }
	}
      }
    }
  }

  /**
   * Method for comparison of two nodes.
   * Used for finding out whether we got to the node that was expanded before or not. 
   * This is one method that has to be redefined in the sub-class.
   *
   * @param node1 a <code>DefaultMutableTreeNode</code> value
   * @param node2 a <code>DefaultMutableTreeNode</code> value
   * @return a <code>boolean</code> value
   */
  abstract protected boolean nodesAreEqual( DefaultMutableTreeNode node1, DefaultMutableTreeNode node2 );

}