keyboard.java

如果你想在自己的计算机游戏中创建音乐编辑器

// Keyboard.java

/*
 * Portions of Keyboard's source code were excerpted from Sun's MidiSynth.java 
 * source file. I've included Sun's original copyright and license, to be fair
 * to Sun.
 *
 * Copyright (c) 1999 Sun Microsystems, Inc. All Rights Reserved.
 *
 * Sun grants you ("Licensee") a non-exclusive, royalty free, license to use,
 * modify and redistribute this software in source and binary code form,
 * provided that i) this copyright notice and license appear on all copies of
 * the software; and ii) Licensee does not utilize the software in a manner
 * which is disparaging to Sun.
 *
 * This software is provided "AS IS," without a warranty of any kind. ALL
 * EXPRESS OR IMPLIED CONDITIONS, REPRESENTATIONS AND WARRANTIES, INCLUDING
 * ANY IMPLIED WARRANTY OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE
 * OR NON-INFRINGEMENT, ARE HEREBY EXCLUDED. SUN AND ITS LICENSORS SHALL NOT
 * BE LIABLE FOR ANY DAMAGES SUFFERED BY LICENSEE AS A RESULT OF USING,
 * MODIFYING OR DISTRIBUTING THE SOFTWARE OR ITS DERIVATIVES. IN NO EVENT WILL
 * SUN OR ITS LICENSORS BE LIABLE FOR ANY LOST REVENUE, PROFIT OR DATA, OR FOR
 * DIRECT, INDIRECT, SPECIAL, CONSEQUENTIAL, INCIDENTAL OR PUNITIVE DAMAGES,
 * HOWEVER CAUSED AND REGARDLESS OF THE THEORY OF LIABILITY, ARISING OUT OF
 * THE USE OF OR INABILITY TO USE SOFTWARE, EVEN IF SUN HAS BEEN ADVISED OF
 * THE POSSIBILITY OF SUCH DAMAGES.
 *
 * This software is not designed or intended for use in on-line control of
 * aircraft, air traffic, aircraft navigation or aircraft communications; or
 * in the design, construction, operation or maintenance of any nuclear
 * facility. Licensee represents and warrants that it will not use or
 * redistribute the Software for such purposes.
 */

import java.awt.*;
import java.awt.event.*;
import java.util.Vector;

import javax.sound.midi.*;
import javax.swing.*;

/*
   This class creates a keyboard component that knows how to play a specific 
   instrument.
*/

public class Keyboard extends JPanel
{
   public final static Color KEY_BLUE = new Color (204, 204, 255);

   public final static int KEY_HEIGHT = 80, KEY_WIDTH = 16;

   private Key theKey;

   private MidiChannel channel;

   private Synthesizer synthesizer;

   private Vector blackKeys = new Vector ();
   private Vector keys = new Vector ();
   private Vector whiteKeys = new Vector ();

   public Keyboard ()
   {
      setLayout (new BorderLayout ());
      setPreferredSize (new Dimension (42*KEY_WIDTH+1, KEY_HEIGHT+1));

      int transpose = 24;  
      int [] whiteIDs = { 0, 2, 4, 5, 7, 9, 11 }; 

      for (int i = 0, x = 0; i < 6; i++) 
      {
           for (int j = 0; j < 7; j++, x += KEY_WIDTH) 
           {
                int keyNum = i * 12 + whiteIDs [j] + transpose;
                whiteKeys.add (new Key (x, 0, KEY_WIDTH, KEY_HEIGHT, keyNum));
           }
      }

      for (int i = 0, x = 0; i < 6; i++, x += KEY_WIDTH) 
      {
           int keyNum = i * 12 + transpose;

           blackKeys.add (new Key ((x += KEY_WIDTH)-4, 0, KEY_WIDTH/2,
                                   KEY_HEIGHT/2, keyNum+1));
           blackKeys.add (new Key ((x += KEY_WIDTH)-4, 0, KEY_WIDTH/2,
                                   KEY_HEIGHT/2, keyNum+3));
           x += KEY_WIDTH;

           blackKeys.add (new Key ((x += KEY_WIDTH)-4, 0, KEY_WIDTH/2,
                          KEY_HEIGHT/2, keyNum+6));
           blackKeys.add (new Key ((x += KEY_WIDTH)-4, 0, KEY_WIDTH/2,
                          KEY_HEIGHT/2, keyNum+8));
           blackKeys.add (new Key ((x += KEY_WIDTH)-4, 0, KEY_WIDTH/2,
                          KEY_HEIGHT/2, keyNum+10));
      }

      keys.addAll (blackKeys);
      keys.addAll (whiteKeys);

      addMouseListener (new MouseAdapter ()
                        {
                            public void mousePressed (MouseEvent e)
                            {
                               // Identify the key that was pressed. A null
                               // value indicates something other than a key
                               // was pressed.

                               theKey = getKey (e.getPoint ());

                               // If a key was pressed ...

                               if (theKey != null)
                               {
                                   // Tell key to start playing note.

                                   theKey.on ();

                                   // Update key's visual appearance.

                                   repaint ();
                               }
                            }

                            public void mouseReleased (MouseEvent e)
                            {
                               if (theKey != null)
                               {
                                   // Tell key to stop playing note.

                                   theKey.off ();

                                   // Update key's visual appearance.

                                   repaint ();
                               }
                            }

                            public void mouseExited (MouseEvent e) 
                            {
                               // This method is called if the mouse is moved
                               // off the keyboard component. If a key was
                               // pressed, we release that key.

                               if (theKey != null)
                               {
                                   // Tell key to stop playing note.

                                   theKey.off ();

                                   // Update key's visual appearance.

                                   repaint ();

                                   // The following assignment is needed so
                                   // that we don't execute the code within
                                   // mouseReleased()'s if statement should we
                                   // release a key after exiting the keyboard 
                                   // component. There is no need to tell the
                                   // key to stop playing a note after we have
                                   // already told it to do so. Furthermore,
                                   // we prevent an unnecessary repaint.

                                   theKey = null;
                               }
                            }

                            public Key getKey (Point point) 
                            {
                               // Identify the key that was clicked.

                               for (int i = 0; i < keys.size (); i++)
                               { 
                                    if (((Key) keys.get (i)).contains (point))
                                        return (Key) keys.get (i);
                               }

                               return null;
                            }
                        });
   }

   public boolean chooseInstrument (int instrumentID)
   {
      if (channel == null)
          return false;

      // Select new instrument based on ID.

      channel.programChange (instrumentID);

      return true;
   }

   public String [] getInstruments ()
   {
      if (synthesizer == null)
          return null;

      Instrument [] instruments = synthesizer.getLoadedInstruments ();

      String [] ins = new String [instruments.length];

      for (int i = 0; i < instruments.length; i++)
           ins [i] = instruments [i].toString ();

      return ins;
   }

   public void paint (Graphics g)
   {
      Graphics2D g2 = (Graphics2D) g;
      Dimension d = getSize ();

      g2.setBackground (getBackground ());
      g2.clearRect (0, 0, d.width, d.height);

      g2.setColor (Color.white);
      g2.fillRect (0, 0, 42*KEY_WIDTH, KEY_HEIGHT);

      for (int i = 0; i < whiteKeys.size (); i++)
      {
           Key key = (Key) whiteKeys.get (i);
           if (key.isNoteOn ()) 
           {
               g2.setColor (KEY_BLUE);
               g2.fill (key);
           }

           g2.setColor (Color.black);
           g2.draw (key);
      }

      for (int i = 0; i < blackKeys.size (); i++) 
      {
           Key key = (Key) blackKeys.get (i);
           if (key.isNoteOn ()) 
           {
               g2.setColor (KEY_BLUE);
               g2.fill (key);

               g2.setColor (Color.black);
               g2.draw (key);
           } 
           else 
           {
               g2.setColor (Color.black);
               g2.fill (key);
           }
      }
   }

   public void turnOff ()
   {
      if (synthesizer == null)
          return;

      // Attempt to unload all instruments.

      synthesizer.unloadAllInstruments (synthesizer.getDefaultSoundbank ());

      // Close the synthesizer, so that it can release any system resources
      // previously acquired during the open() call.

      synthesizer.close ();
      synthesizer = null;
   }

   public boolean turnOn ()
   {
      try
      {
          if (synthesizer == null) 
          {
              // Obtain the default synthesizer.

              if ((synthesizer = MidiSystem.getSynthesizer ()) == null)
                  return false;

              // Open the synthesizer, so that it can acquire any system
              // resources and become operational.

              synthesizer.open ();

          }
      }
      catch (Exception e)
      {
          e.printStackTrace();
          return false;
      }

      // Attempt load all instruments.

      synthesizer.loadAllInstruments (synthesizer.getDefaultSoundbank ());

      // Obtain the set of MIDI channels controlled by the synthesizer.

      MidiChannel [] midiChannels = synthesizer.getChannels ();

      // There must be at least one channel. Furthermore, we assume that the
      // first channel is used by the synthesizer. If you run into a problem,
      // use the index (other than 0) of the first non-null midiChannels
      // entry.

      if (midiChannels.length == 0 || midiChannels [0] == null)
      {
          synthesizer.close ();
          synthesizer = null;
          return false;
      }

      // Identify the channel to which note messages are sent.

      channel = midiChannels [0];

      return true;
   }

   /*
      This inner class describes an instrument key that knows how to start
      sounding and stop sounding its note. Furthermore, each key knows its
      size and location.
   */

   class Key extends Rectangle 
   {
      final static int ON = 0, OFF = 1, VELOCITY = 64;

      int kNum, noteState = OFF;

      public Key (int x, int y, int width, int height, int num) 
      {
         super (x, y, width, height);
         kNum = num;
      }

      public boolean isNoteOn () 
      {
          return noteState == ON;
      }

      public void off () 
      {
         setNoteState (OFF);
         //Keyboard.this.repaint ();

         // Send the key number to the channel so the note stops sounding.
         // Also send a keyup VELOCITY, which might affect how quickly the
         // note decays.

         if (channel != null)
             channel.noteOff (kNum, VELOCITY);
      }

      public void on () 
      {
         setNoteState (ON);
         //Keyboard.this.repaint ();

         // Send the key number (0 - 127, where 60 indicates Middle C) to the
         // channel so the note starts to sound. Also send a keydown VELOCITY,
         // which indicates the speed at which a key was pressed (the loudness
         // or volume of the note).

         if (channel != null)
             channel.noteOn (kNum, VELOCITY);
      }

      public void setNoteState (int state) 
      {
         noteState = state;
      }
   }
}