composemgr.java

一个用java写的mail.里面的代码值得我们去研究！学习。

/*
** $Id: ComposeMgr.java,v 1.4 2001/05/07 12:37:21 kunugi Exp $
**
** Copyright (c) 2000-2001 Jeff Gay
** on behalf of ICEMail.org <http://www.icemail.org>
** Copyright (c) 2000 by Timothy Gerard Endres
** 
** This program is free software.
** 
** You may redistribute it and/or modify it under the terms of the GNU
** General Public License as published by the Free Software Foundation.
** Version 2 of the license should be included with this distribution in
** the file LICENSE, as well as License.html. If the license is not
** included with this distribution, you may find a copy at the FSF web
** site at 'www.gnu.org' or 'www.fsf.org', or you may write to the
** Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139 USA.
**
** THIS SOFTWARE IS PROVIDED AS-IS WITHOUT WARRANTY OF ANY KIND,
** NOT EVEN THE IMPLIED WARRANTY OF MERCHANTABILITY. THE AUTHOR
** OF THIS SOFTWARE, ASSUMES _NO_ RESPONSIBILITY FOR ANY
** CONSEQUENCE RESULTING FROM THE USE, MODIFICATION, OR
** REDISTRIBUTION OF THIS SOFTWARE. 
*/

package org.icemail.mail;

import java.util.Vector;
import java.util.Enumeration;

import javax.mail.Message;

import org.icemail.Package;


/**
 * This is a manager for all composition frames.
 * <p>
 * At this time, JFrame is known to leak memory, so all ComposeFrames
 * are managed, and re-used.
 * <p>
 * Note: A side effect is that composition frames are faster now.
 *
 * @see ComposeFrame
 */
public class ComposeMgr
{
  private static final int Debug_ = Package.DEBUG ? Package.getLevel( "ComposeMgr" ) : 0;

  private static ComposeMgr Instance_ = null;

  private Vector            frames_ = null;

  /**
   * Default constructor, private to disable multiple instantiations.
   */
  private
  ComposeMgr()
  { }

  /**
   * Get the SINGLE instance of the manager, creating it if necessary.
   *
   * @return the SINGLE instance of the manager
   */
  public static synchronized ComposeMgr
  getInstance() {
    if ( ComposeMgr.Instance_ == null ) {
      ComposeMgr.Instance_ = new ComposeMgr();
      ComposeMgr.Instance_.frames_ = new Vector();
    }
    return ComposeMgr.Instance_;
  }

  /**
   * Get a composition frame for use in editing a message, creating it if necessary.
   *
   * @return a composition frame for use in editing a message
   */
  public synchronized ComposeFrame
  getComposeFrame() {
    if ( Package.DEBUG && Package.isTraceable( "ComposeMgr" ) ) {
      System.out.println( "ComposeMgr.getComposeFrame(): " + frames_.size() );
    }

    ComposeFrame result = null;

    for ( int i = 0, sz = frames_.size() ; i < sz ; ++i ) {
      ComposeFrame xframe = (ComposeFrame)frames_.elementAt( i );

      if ( ! xframe.isEnabled() ) {
        if ( Package.DEBUG && Debug_ > 0 ) {
          System.out.println( "ComposeMgr.getComposeFrame(): re-using disabled ComposeFrame" );
        }
        result = xframe;
        break;
      }
    }

    if ( result == null ) {
      if ( Package.DEBUG && Debug_ > 0 ) {
        System.out.println( "ComposeMgr.getComposeFrame(): creating new ComposeFrame" );
      }
      ComposeFrame xframe = new ComposeFrame();
      frames_.addElement( xframe );
      result = xframe;
    }

    return result;
  }

  /**
   * Determine if there are compositions being performed.
   * Composition frames that are 'enabled' are considered to be in use.
   * <p>
   * Note: Because ComposeFrame's are disabled by a separate thread, this
   * method may return true if a frame has just been closed.
   *
   * @return true if any composition frame is being used
   */
  public synchronized boolean
  hasOpenWindows() {
    if ( Package.DEBUG && Package.isTraceable( "ComposeMgr" ) ) {
      System.err.println( "ComposeMgr.hasOpenWindows()" );
    }

    boolean result = false;

    for ( int i = 0, sz = frames_.size() ; i < sz ; ++i ) {
      ComposeFrame xframe = (ComposeFrame)frames_.elementAt( i );

      if ( xframe.isEnabled() ) {
        result = true;
        break;
      }
    }

    return result;
  }

  /**
   * Utility method to close all composition frames before exiting.
   *
   * @see ICEMail
   */
  public synchronized void
  closeAllFrames() {
    if ( Package.DEBUG && Package.isTraceable( "ComposeMgr" ) ) {
      System.err.println( "ComposeMgr.closeAllFrames()" );
    }

    for ( int i = 0, sz = frames_.size() ; i < sz ; ++i ) {
      ComposeFrame xframe = (ComposeFrame)frames_.elementAt( i );

      if ( xframe.isEnabled() ) {
        xframe.toFront();
        xframe.dispose();
      }
    }
  }
}