'javax.sound.midi for Android' example code

InitializeDestroy.java

public class MidiPlayingFragment extends Fragment {
    private Sequencer sequencer = null;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        MidiSystem.initialize(getActivity());

        try {
            sequencer = MidiSystem.getSequencer();
        } catch (MidiUnavailableException e) {
            Log.e("USB MIDI Sample", e.getMessage(), e);
        }
    }

    @Override
    public void onDestroy() {
        super.onDestroy();

        if (sequencer != null) {
            if (sequencer.isOpen()) {
                sequencer.close();
            }
            sequencer = null;
        }

        MidiSystem.terminate();
    }

StartStopPlaying.java

        Button playButton = (Button) inflated.findViewById(R.id.playButton);
        playButton.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {

                if (sequencer != null) {
                    try {
                        sequencer.open();
                    } catch (MidiUnavailableException e) {
                        Log.e("USB MIDI Sample", e.getMessage(), e);
                    }

                    try {
                        try {
                            Sequence sequence = MidiSystem.getSequence(getActivity().getAssets().open("furusato.mid"));

                            sequencer.setSequence(sequence);
                            sequencer.stop();
                            sequencer.setTickPosition(0);
                            sequencer.setLoopStartPoint(0);
                            sequencer.start();
                        } catch (IOException e) {
                            Log.e("USB MIDI Sample", e.getMessage(), e);
                        }
                    } catch (InvalidMidiDataException e) {
                        Log.e("USB MIDI Sample", e.getMessage(), e);
                    }
                }
            }
        });
        
        Button stopButton = (Button) inflated.findViewById(R.id.stopButton);
        stopButton.setOnClickListener(new OnClickListener() {
            
            @Override
            public void onClick(View v) {
                if (sequencer != null) {
                    sequencer.stop();
                }
            }
        });

How can MidiSystem.initialize(getActivity()); work?