Beatbox Basic version

BeatBox.java

// make a beatbox

import java.awt.*;
import javax.swing.*; 
import javax.sound.midi.*; 
import java.util.*;
import java.awt.event.*;

public class BeatBox {

	JPanel mainPanel;
	ArrayList<JCheckBox> checkboxList; // store checkboxes in array
	Sequencer sequencer;
	Sequence sequence;
	Track track;
	JFrame theFrame;

	String[] instrumentNames = { "Bass Drum", "Closed Hi-Hat", "Open Hi-Hat", 
		"Acoustic Snare", "Crash Cymbal", "Hand Clap", "High Tom", "Hi Bongo", 
		"Maracas", "Whistle", "Low Conga", "Cowbell", "Vibraslap",
		"Low-mid Tom", "High Agogo", "Open Hi Conga"};
	int[] instruments = {35,42,46,38,49,39,50,60,70,72,64,56,58,47,67,63};

	public static void main (String[] args) {
		new BeatBox().buildGUI();
	}

	public void buildGUI() {
		theFrame = new JFrame("Michelle's BeatBox");
		theFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		BorderLayout layout = new BorderLayout();
		JPanel background = new JPanel(layout);
		background.setBorder(BorderFactory.createEmptyBorder(10,10,10,10));

		checkboxList = new ArrayList<JCheckBox>();
		Box buttonBox = new Box(BoxLayout.Y_AXIS);

		JButton start = new JButton("Play");
		start.addActionListener(new MyStartListener());
		buttonBox.add(start);

		JButton stop = new JButton("Stop");
		stop.addActionListener(new MyStopListener());
		buttonBox.add(stop);

		JButton upTempo = new JButton("Faster");
		upTempo.addActionListener(new MyUpTempoListener());
		buttonBox.add(upTempo);

		JButton downTempo = new JButton("Slower");
		downTempo.addActionListener(new MyDownTempoListener());
		buttonBox.add(downTempo);

		Box nameBox = new Box(BoxLayout.Y_AXIS);
		for (int i = 0; i<16; i++){
			nameBox.add(new Label(instrumentNames[i]));
		}

		background.add(BorderLayout.EAST, buttonBox);
		background.add(BorderLayout.WEST, nameBox);

		theFrame.getContentPane().add(background);

		GridLayout grid = new GridLayout(16,16);
		grid.setVgap(1);
		grid.setHgap(2);
		mainPanel = new JPanel(grid);
		background.add(BorderLayout.CENTER, mainPanel);

		for (int i = 0; i < 256; i++) {
			JCheckBox c = new JCheckBox();
			c.setSelected(false);
			checkboxList.add(c);
			mainPanel.add(c);
		}
		setUpMidi();

		theFrame.setBounds(50,50,300,300);
		theFrame.pack();
		theFrame.setVisible(true);

	}


	public void setUpMidi() {
		try {
			sequencer = MidiSystem.getSequencer();
			sequencer.open();
			sequence = new Sequence(Sequence.PPQ,4);
			track = sequence.createTrack();
			sequencer.setTempoInBPM(120); 
		}
		catch (Exception e) {e.printStackTrace();}
	}

	// turn checkbox state into MIDI events and add to track
	public void buildTrackAndStart() {
		int[] trackList = null;
		// make a 16 element array to hold values for one instrument, across
		// 16 beats

		sequence.deleteTrack(track);
		track = sequence.createTrack();
		// get rid of old track, make fresh

		for (int i = 0; i<16; i++) {
			trackList = new int[16];
			int key = instruments[i]; // represent each instrument

			for (int j = 0; j < 16; j++) {
				JCheckBox jc = (JCheckBox) checkboxList.get(j + (16*i));
				if ( jc.isSelected()) {
					trackList[j] = key;
				} else {
					trackList[j]= 0;
				}
			}
			makeTracks(trackList);
			track.add(makeEvent(176, 1, 127, 0, 16));
		}
		track.add(makeEvent(192,9,1,0,15));
		try {
			sequencer.setSequence(sequence);
			sequencer.setLoopCount(sequencer.LOOP_CONTINUOUSLY);
			sequencer.start();
			sequencer.setTempoInBPM(120);
		} catch (Exception e) {e.printStackTrace();}

	}

	// four inner classes listeners for buttons
	public class MyStartListener implements ActionListener {
		public void actionPerformed(ActionEvent a){
			buildTrackAndStart();
		}
	}
	public class MyStopListener implements ActionListener {
		public void actionPerformed(ActionEvent a){
			sequencer.stop();
		}
	}
	public class MyUpTempoListener implements ActionListener {
		public void actionPerformed(ActionEvent a){
			float tempoFactor = sequencer.getTempoFactor();
			sequencer.setTempoFactor((float) (tempoFactor * 1.1));
		}
	}
	public class MyDownTempoListener implements ActionListener {
		public void actionPerformed(ActionEvent a){
			float tempoFactor = sequencer.getTempoFactor();
			sequencer.setTempoFactor((float) (tempoFactor * 0.9));
		}
	}

	// make events for one instrument at a time
	public void makeTracks(int[] list){
		for (int i= 0; i<16; i++) {
			int key = list[i];

			if (key != 0){
				track.add(makeEvent(144,9,key,100,i));
				track.add(makeEvent(128,9,key,100,i+1));
				// make NOTE ON and NOTE OFF events and add to track
			}
		}
	}
	public MidiEvent makeEvent(int comd, int chan, int one, int two, int tick){
		MidiEvent event = null;
		try {
			ShortMessage a = new ShortMessage();
			a.setMessage(comd,chan,one,two);
			event = new MidiEvent(a, tick);

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