我希望在播放的MIDI序列中收到音符开/关事件的通知，以便在基于屏幕的（钢琴）键盘上显示音符。
下面的代码在播放MIDI文件时会添加MetaEventListener和ControllerEventListener，但只会在曲目的开头和结尾显示一些消息。
我们怎样才能听取关于＆amp;关注MIDI事件？
import java.io.File;
import javax.sound.midi.*;
import javax.swing.JOptionPane;
class PlayMidi {
public static void main(String[] args) throws Exception {
/* This MIDI file can be found at..
https://drive.google.com/open?id=0B5B9wDXIGw9lR2dGX005anJsT2M&authuser=0
*/
File path = new File("I:\\projects\\EverLove.mid");
Sequence sequence = MidiSystem.getSequence(path);
Sequencer sequencer = MidiSystem.getSequencer();
sequencer.open();
MetaEventListener mel = new MetaEventListener() {
@Override
public void meta(MetaMessage meta) {
final int type = meta.getType();
System.out.println("MEL - type: " + type);
}
};
sequencer.addMetaEventListener(mel);
int[] types = new int[128];
for (int ii = 0; ii < 128; ii++) {
types[ii] = ii;
}
ControllerEventListener cel = new ControllerEventListener() {
@Override
public void controlChange(ShortMessage event) {
int command = event.getCommand();
if (command == ShortMessage.NOTE_ON) {
System.out.println("CEL - note on!");
} else if (command == ShortMessage.NOTE_OFF) {
System.out.println("CEL - note off!");
} else {
System.out.println("CEL - unknown: " + command);
}
}
};
int[] listeningTo = sequencer.addControllerEventListener(cel, types);
for (int ii : listeningTo) {
System.out.println("Listening To: " + ii);
}
sequencer.setSequence(sequence);
sequencer.start();
JOptionPane.showMessageDialog(null, "Exit this dialog to end");
sequencer.stop();
sequencer.close();
}
}
答案 0 :(得分：6)
这是接受答案的第一个建议的实现。它将显示一个选项窗格确认对话框，指示是否添加新轨道以保存与NOTE_ON＆amp;对应的元事件。每条现有曲目的NOTE_OFF条消息。
如果用户选择这样做，他们会在整个MIDI序列播放过程中看到Meta事件。
import java.io.File;
import javax.sound.midi.*;
import javax.swing.JOptionPane;
class PlayMidi {
/** Iterates the MIDI events of the first track and if they are a
* NOTE_ON or NOTE_OFF message, adds them to the second track as a
* Meta event. */
public static final void addNotesToTrack(
Track track,
Track trk) throws InvalidMidiDataException {
for (int ii = 0; ii < track.size(); ii++) {
MidiEvent me = track.get(ii);
MidiMessage mm = me.getMessage();
if (mm instanceof ShortMessage) {
ShortMessage sm = (ShortMessage) mm;
int command = sm.getCommand();
int com = -1;
if (command == ShortMessage.NOTE_ON) {
com = 1;
} else if (command == ShortMessage.NOTE_OFF) {
com = 2;
}
if (com > 0) {
byte[] b = sm.getMessage();
int l = (b == null ? 0 : b.length);
MetaMessage metaMessage = new MetaMessage(com, b, l);
MidiEvent me2 = new MidiEvent(metaMessage, me.getTick());
trk.add(me2);
}
}
}
}
public static void main(String[] args) throws Exception {
/* This MIDI file can be found at..
https://drive.google.com/open?id=0B5B9wDXIGw9lR2dGX005anJsT2M&authuser=0
*/
File path = new File("I:\\projects\\EverLove.mid");
Sequence sequence = MidiSystem.getSequence(path);
Sequencer sequencer = MidiSystem.getSequencer();
sequencer.open();
MetaEventListener mel = new MetaEventListener() {
@Override
public void meta(MetaMessage meta) {
final int type = meta.getType();
System.out.println("MEL - type: " + type);
}
};
sequencer.addMetaEventListener(mel);
int[] types = new int[128];
for (int ii = 0; ii < 128; ii++) {
types[ii] = ii;
}
ControllerEventListener cel = new ControllerEventListener() {
@Override
public void controlChange(ShortMessage event) {
int command = event.getCommand();
if (command == ShortMessage.NOTE_ON) {
System.out.println("CEL - note on!");
} else if (command == ShortMessage.NOTE_OFF) {
System.out.println("CEL - note off!");
} else {
System.out.println("CEL - unknown: " + command);
}
}
};
int[] listeningTo = sequencer.addControllerEventListener(cel, types);
StringBuilder sb = new StringBuilder();
for (int ii = 0; ii < listeningTo.length; ii++) {
sb.append(ii);
sb.append(", ");
}
System.out.println("Listenning to: " + sb.toString());
int mirror = JOptionPane.showConfirmDialog(
null,
"Add note on/off messages to another track as meta messages?",
"Confirm Mirror",
JOptionPane.OK_CANCEL_OPTION);
if (mirror == JOptionPane.OK_OPTION) {
Track[] tracks = sequence.getTracks();
Track trk = sequence.createTrack();
for (Track track : tracks) {
addNotesToTrack(track, trk);
}
}
sequencer.setSequence(sequence);
sequencer.start();
JOptionPane.showMessageDialog(null, "Exit this dialog to end");
sequencer.stop();
sequencer.close();
}
}
import java.awt.*;
import java.awt.event.*;
import java.awt.geom.*;
import javax.swing.*;
import javax.swing.border.EmptyBorder;
import javax.sound.midi.*;
import java.util.ArrayList;
import java.io.*;
import java.net.URL;
public class MidiPianola {
private JComponent ui = null;
public static final int OTHER = -1;
public static final int NOTE_ON = 1;
public static final int NOTE_OFF = 2;
private OctaveComponent[] octaves;
Sequencer sequencer;
int startOctave = 0;
int numOctaves = 0;
MidiPianola(int startOctave, int numOctaves)
throws MidiUnavailableException {
this.startOctave = startOctave;
this.numOctaves = numOctaves;
initUI();
}
public void openMidi(URL url)
throws InvalidMidiDataException, IOException {
openMidi(url.openStream());
}
public void openMidi(InputStream is)
throws InvalidMidiDataException, IOException {
Sequence sequence = MidiSystem.getSequence(is);
Track[] tracks = sequence.getTracks();
Track trk = sequence.createTrack();
for (Track track : tracks) {
addNotesToTrack(track, trk);
}
sequencer.setSequence(sequence);
startMidi();
}
public void startMidi() {
sequencer.start();
}
public void stopMidi() {
sequencer.stop();
}
public void closeSequencer() {
sequencer.close();
}
private void handleNote(final int command, int note) {
OctaveComponent octave = getOctaveForNote(note);
PianoKey key = octave.getKeyForNote(note);
if (command == NOTE_ON) {
key.setPressed(true);
} else if (command == NOTE_OFF) {
key.setPressed(false);
}
ui.repaint();
}
private OctaveComponent getOctaveForNote(int note) {
return octaves[(note / 12) - startOctave];
}
public void initUI() throws MidiUnavailableException {
if (ui != null) {
return;
}
sequencer = MidiSystem.getSequencer();
MetaEventListener mel = new MetaEventListener() {
@Override
public void meta(MetaMessage meta) {
final int type = meta.getType();
byte b = meta.getData()[1];
int i = (int) (b & 0xFF);
handleNote(type, i);
}
};
sequencer.addMetaEventListener(mel);
sequencer.open();
ui = new JPanel(new BorderLayout(4, 4));
ui.setBorder(new EmptyBorder(4, 4, 4, 4));
JPanel keyBoard = new JPanel(new GridLayout(1, 0));
ui.add(keyBoard, BorderLayout.CENTER);
int end = startOctave + numOctaves;
octaves = new OctaveComponent[end - startOctave];
for (int i = startOctave; i < end; i++) {
octaves[i - startOctave] = new OctaveComponent(i);
keyBoard.add(octaves[i - startOctave]);
}
JToolBar tools = new JToolBar();
tools.setFloatable(false);
ui.add(tools, BorderLayout.PAGE_START);
tools.setFloatable(false);
Action open = new AbstractAction("Open") {
JFileChooser fileChooser = new JFileChooser();
@Override
public void actionPerformed(ActionEvent e) {
int result = fileChooser.showOpenDialog(ui);
if (result == JFileChooser.APPROVE_OPTION) {
File f = fileChooser.getSelectedFile();
try {
openMidi(f.toURI().toURL());
} catch (Exception ex) {
ex.printStackTrace();
}
}
}
};
tools.add(open);
Action rewind = new AbstractAction("Rewind") {
@Override
public void actionPerformed(ActionEvent e) {
sequencer.setTickPosition(0);
}
};
tools.add(rewind);
Action play = new AbstractAction("Play") {
@Override
public void actionPerformed(ActionEvent e) {
startMidi();
}
};
tools.add(play);
Action stop = new AbstractAction("Stop") {
@Override
public void actionPerformed(ActionEvent e) {
stopMidi();
}
};
tools.add(stop);
}
public JComponent getUI() {
return ui;
}
/**
* Iterates the MIDI events of the first track, and if they are a NOTE_ON or
* NOTE_OFF message, adds them to the second track as a Meta event.
*/
public static final void addNotesToTrack(
Track track,
Track trk) throws InvalidMidiDataException {
for (int ii = 0; ii < track.size(); ii++) {
MidiEvent me = track.get(ii);
MidiMessage mm = me.getMessage();
if (mm instanceof ShortMessage) {
ShortMessage sm = (ShortMessage) mm;
int command = sm.getCommand();
int com = OTHER;
if (command == ShortMessage.NOTE_ON) {
com = NOTE_ON;
} else if (command == ShortMessage.NOTE_OFF) {
com = NOTE_OFF;
}
if (com > OTHER) {
byte[] b = sm.getMessage();
int l = (b == null ? 0 : b.length);
MetaMessage metaMessage = new MetaMessage(
com,
b,
l);
MidiEvent me2 = new MidiEvent(metaMessage, me.getTick());
trk.add(me2);
}
}
}
}
public static void main(String[] args) {
Runnable r = new Runnable() {
@Override
public void run() {
try {
try {
UIManager.setLookAndFeel(
UIManager.getSystemLookAndFeelClassName());
} catch (Exception useDefault) {
}
SpinnerNumberModel startModel =
new SpinnerNumberModel(2,0,6,1);
JOptionPane.showMessageDialog(
null,
new JSpinner(startModel),
"Start Octave",
JOptionPane.QUESTION_MESSAGE);
SpinnerNumberModel octavesModel =
new SpinnerNumberModel(5,5,11,1);
JOptionPane.showMessageDialog(
null,
new JSpinner(octavesModel),
"Number of Octaves",
JOptionPane.QUESTION_MESSAGE);
final MidiPianola o = new MidiPianola(
startModel.getNumber().intValue(),
octavesModel.getNumber().intValue());
WindowListener closeListener = new WindowAdapter() {
@Override
public void windowClosing(WindowEvent e) {
o.closeSequencer();
}
};
JFrame f = new JFrame("MIDI Pianola");
f.addWindowListener(closeListener);
f.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
f.setLocationByPlatform(true);
f.setContentPane(o.getUI());
f.setResizable(false);
f.pack();
f.setVisible(true);
} catch (MidiUnavailableException ex) {
ex.printStackTrace();
} catch (InvalidMidiDataException ex) {
ex.printStackTrace();
} catch (IOException ex) {
ex.printStackTrace();
}
}
};
SwingUtilities.invokeLater(r);
}
}
class OctaveComponent extends JPanel {
int octave;
ArrayList<PianoKey> keys;
PianoKey selectedKey = null;
public OctaveComponent(int octave) {
this.octave = octave;
init();
}
public PianoKey getKeyForNote(int note) {
int number = note % 12;
return keys.get(number);
}
@Override
public void paintComponent(Graphics g) {
Graphics2D g2 = (Graphics2D) g;
for (PianoKey key : keys) {
key.draw(g2);
}
}
public static final Shape
removeArrayFromShape(Shape shape, Shape[] shapes) {
Area a = new Area(shape);
for (Shape sh : shapes) {
a.subtract(new Area(sh));
}
return a;
}
public final Shape getEntireBounds() {
Area a = new Area();
for (PianoKey key : keys) {
a.add(new Area(key.keyShape));
}
return a;
}
@Override
public Dimension getPreferredSize() {
Shape sh = getEntireBounds();
Rectangle r = sh.getBounds();
Dimension d = new Dimension(r.x + r.width, r.y + r.height + 1);
return d;
}
public void init() {
keys = new ArrayList<PianoKey>();
int w = 30;
int h = 200;
int x = 0;
int y = 0;
int xs = w - (w / 3);
Shape[] sharps = new Shape[5];
int hs = h * 3 / 5;
int ws = w * 2 / 3;
sharps[0] = new Rectangle2D.Double(xs, y, ws, hs);
xs += w;
sharps[1] = new Rectangle2D.Double(xs, y, ws, hs);
xs += 2 * w;
sharps[2] = new Rectangle2D.Double(xs, y, ws, hs);
xs += w;
sharps[3] = new Rectangle2D.Double(xs, y, ws, hs);
xs += w;
sharps[4] = new Rectangle2D.Double(xs, y, ws, hs);
Shape[] standards = new Shape[7];
for (int ii = 0; ii < standards.length; ii++) {
Shape shape = new Rectangle2D.Double(x, y, w, h);
x += w;
standards[ii] = removeArrayFromShape(shape, sharps);
}
int note = 0;
int ist = 0;
int ish = 0;
keys.add(new PianoKey(standards[ist++], (octave * 12) + note++, "C", this));
keys.add(new PianoKey(sharps[ish++], (octave * 12) + note++, "C#", this));
keys.add(new PianoKey(standards[ist++], (octave * 12) + note++, "D", this));
keys.add(new PianoKey(sharps[ish++], (octave * 12) + note++, "D#", this));
keys.add(new PianoKey(standards[ist++], (octave * 12) + note++, "E", this));
keys.add(new PianoKey(standards[ist++], (octave * 12) + note++, "F", this));
keys.add(new PianoKey(sharps[ish++], (octave * 12) + note++, "F#", this));
keys.add(new PianoKey(standards[ist++], (octave * 12) + note++, "G", this));
keys.add(new PianoKey(sharps[ish++], (octave * 12) + note++, "G#", this));
keys.add(new PianoKey(standards[ist++], (octave * 12) + note++, "A", this));
keys.add(new PianoKey(sharps[ish++], (octave * 12) + note++, "A#", this));
keys.add(new PianoKey(standards[ist++], (octave * 12) + note++, "B", this));
}
}
class PianoKey {
Shape keyShape;
int number;
String name;
Component component;
boolean pressed = false;
PianoKey(Shape keyShape, int number, String name, Component component) {
this.keyShape = keyShape;
this.number = number;
this.name = name;
this.component = component;
}
public void draw(Graphics2D g) {
if (name.endsWith("#")) {
g.setColor(Color.BLACK);
} else {
g.setColor(Color.WHITE);
}
g.fill(keyShape);
g.setColor(Color.GRAY);
g.draw(keyShape);
if (pressed) {
Rectangle r = keyShape.getBounds();
GradientPaint gp = new GradientPaint(
r.x,
r.y,
new Color(255, 225, 0, 40),
r.x,
r.y + (int) r.getHeight(),
new Color(255, 225, 0, 188));
g.setPaint(gp);
g.fill(keyShape);
g.setColor(Color.GRAY);
g.draw(keyShape);
}
}
public boolean isPressed() {
return pressed;
}
public void setPressed(boolean pressed) {
this.pressed = pressed;
}
}
答案 1 :(得分：4)
我会注意看看是否有比我提出的两个建议更好的答案，这些建议显然不太理想。
我自己也没有用MIDI做过很多事情。我偶尔会导入MIDI乐谱并删除大部分信息，将其转换为我为自己的音频需求编写的事件系统（触发我写的FM合成器）。
答案 2 :(得分：1)
答案here。像这样：
class MidiPlayer implements Receiver {
private Receiver myReceiver;
void play() {
Sequencer sequencer = MidiSystem.getSequencer();
...
// Save the original receiver
this.myReceiver = sequencer.getReceiver();
// Override the receiver
sequencer.getTransmitter().setReceiver(this);
sequencer.start();
}
@Override
public void send(MidiMessage msg, long tstamp) {
// Send the message to the original receiver
this.myReceiver.send(msg, tstamp);
// Process the message
if (msg instanceof ShortMessage) {
ShortMessage shortMsg = (ShortMessage) msg;
if (shortMsg.getCommand() == ShortMessage.NOTE_ON) {
System.out.printf("NOTE ON\n");
}
}
...
}