MidiDroid

MIDI library for Android, ready to use in Android Studio projects.

Description

This Midi library is an update of Android MIDI Library, by Alex Leffelman. Now it is packaged as a convenient Android Library, instead of the original Eclipse project. However, it is a stand-alone Java library with no Android-specific dependencies or considerations. It 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.

Usage

Step 1. Add JitPack to your root build.gradle at the end of repositories:

allprojects {
		repositories {
			...
			maven { url "https://jitpack.io" }
		}
	}

Step 2. Add the dependency in your module build.gradle:

dependencies {
        compile 'com.github.pdrogfer:MidiDroid:v1.0'
}

Use it and enjoy. Contributions and pull requests are certainly welcome.

Examples:

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");
        }
    }
}

License

Apache 2.0

babua/MidiDroid