Android MIDI Library
This project is mainly for use with Android applications that do not have access to Java's javax.sound.midi library. However, it is a stand-alone Java library with no Android-specific dependencies or considerations.
This code provides an interface to read, manipulate, and write MIDI files. "Playback" is supported as a real-time event dispatch system. This library does NOT include actual audio playback or device interfacing.
Example Usage:
Reading and Writing a MIDI file:
File input = new File("example.mid");
MidiFile midi = new MidiFile(input);
... File output = new File("output.mid");
midi.writeToFile(output);
Manipulating a MIDI file's data:
Removing a track:
midi.removeTrack(2);
Removing any event that is not a note from track 1:
MidiTrack track = midi.getTracks().get(1);
Iterator<MidiEvent> it = track.getEvents().iterator();
List<MidiEvent> eventsToRemove = new ArrayList<MidiEvent>();
while(it.hasNext()) {
MidiEvent event = it.next();
if(!(event instanceof NoteOn) && !(event instanceof NoteOff))
{
eventsToRemove.add(event);
}
}
for(MidiEvent event : eventsToRemove) {
track.removeEvent(event);
}
Reducing the tempo by half:
MidiTrack tempoTrack = midi.getTracks().get(0);
Iterator<MidiEvent> it = tempoTrack.getEvents().iterator();
while(it.hasNext()) {
MidiEvent event = it.next();
if(event instanceof Tempo)
{
Tempo tempoEvent = (Tempo)event;
tempoEvent.setBpm(tempo.getBpm() / 2);
}
}
Composing a new MIDI file:
// 1. Create some MidiTracks MidiTrack tempoTrack = new MidiTrack();
MidiTrack noteTrack = new MidiTrack();
// 2. Add events to the tracks // Track 0 is the tempo map TimeSignature ts = new TimeSignature();
ts.setTimeSignature(4, 4, TimeSignature.DEFAULT_METER, TimeSignature.DEFAULT_DIVISION);
Tempo tempo = new Tempo();
tempo.setBpm(228);
tempoTrack.insertEvent(ts);
tempoTrack.insertEvent(tempo);
// Track 1 will have some notes in it final int NOTE_COUNT = 80; for(int i = 0; i < NOTE_COUNT; i++) {
int channel = 0;
int pitch = 1 + i;
int velocity = 100;
long tick = i * 480;
long duration = 120;
noteTrack.insertNote(channel, pitch, velocity, tick, duration);
}
// 3. Create a MidiFile with the tracks we created List<MidiTrack> tracks = new ArrayList<MidiTrack>();
tracks.add(tempoTrack);
tracks.add(noteTrack);
MidiFile midi = new MidiFile(MidiFile.DEFAULT_RESOLUTION, tracks);
// 4. Write the MIDI data to a file File output = new File("exampleout.mid");
try {
midi.writeToFile(output);
}
catch(IOException e) {
System.err.println(e);
}
Listening for and processing MIDI events
// Create a new MidiProcessor: MidiProcessor processor = new MidiProcessor(midi);
// Register for the events you're interested in: EventPrinter ep = new EventPrinter("Individual Listener");
processor.registerEventListener(ep, Tempo.class);
processor.registerEventListener(ep, NoteOn.class);
// or listen for all events: EventPrinter ep2 = new EventPrinter("Listener For All");
processor.registerEventListener(ep2, MidiEvent.class);
// Start the processor: processor.start();
// This class will print any event it receives to the console public class EventPrinter implements MidiEventListener {
private String mLabel;
public EventPrinter(String label)
{
mLabel = label;
}
@Override
public void onStart(boolean fromBeginning)
{
if(fromBeginning)
{
System.out.println(mLabel + " Started!");
}
else
{
System.out.println(mLabel + " resumed");
}
}
@Override
public void onEvent(MidiEvent event, long ms)
{
System.out.println(mLabel + " received event: " + event);
}
@Override
public void onStop(boolean finished)
{
if(finished)
{
System.out.println(mLabel + " Finished!");
}
else
{
System.out.println(mLabel + " paused");
}
}
}