java - 为什么我的 MIDI 程序没有完成/关闭？

Question

我有这个简单的程序，它使用 MIDI 只播放一个音符。问题是，即使它播放了程序继续运行的音符，但我不知道为什么。有帮助吗？

    Sequencer sequencer = MidiSystem.getSequencer();
    sequencer.open();
    Sequence sequence = new Sequence(Sequence.PPQ, 1);
    Track track = sequence.createTrack();

    ShortMessage noteOnMsg = new ShortMessage();
    noteOnMsg.setMessage(ShortMessage.NOTE_ON, 0, 60, 100);
    ShortMessage noteOffMsg = new ShortMessage();
    noteOffMsg.setMessage(ShortMessage.NOTE_OFF, 0, 60, 100);

    track.add(new MidiEvent(noteOnMsg, 0));
    track.add(new MidiEvent(noteOffMsg, 120));
    sequencer.setSequence(sequence);

    sequencer.start();
    Thread.sleep(5000);
    sequencer.stop();

Answer 1

Sequencer 需要关闭。一种选择是将 sequencer.close() 添加到代码的末尾，但由于 Sequencer 实现了 AutoCloseable，更好的方法是将其放在 try-with-resources 子句中:

try (Sequencer sequencer = MidiSystem.getSequencer()) {
    sequencer.open();
    Sequence sequence = new Sequence(Sequence.PPQ, 1);
    Track track = sequence.createTrack();

    ShortMessage noteOnMsg = new ShortMessage();
    noteOnMsg.setMessage(ShortMessage.NOTE_ON, 0, 60, 100);
    ShortMessage noteOffMsg = new ShortMessage();
    noteOffMsg.setMessage(ShortMessage.NOTE_OFF, 0, 60, 100);

    track.add(new MidiEvent(noteOnMsg, 0));
    track.add(new MidiEvent(noteOffMsg, 120));
    sequencer.setSequence(sequence);

    sequencer.start();
    Thread.sleep(5000);
    sequencer.stop();
}