Java MIDI 音序器永无止境

Posted 2023-02-16

【中文标题】Java MIDI 音序器永无止境

【英文标题】：Java MIDI sequencer never ends

【发布时间】：2020-01-05 10:56:09

【问题描述】：

我正在运行教程中的一些 MIDI 代码，但程序永远不会终止。似乎 MIDI 音序器从未停止运行，即使它报告长度为 0.625 秒。

我是否需要做其他事情才能使音序器停止？

import javax.sound.midi.*;

public class MyMidiPlayer 
    public static void main(String[] args)
    
        MyMidiPlayer player = new MyMidiPlayer();
        player.setUpPlayer(4);
    

    public void setUpPlayer(int numOfNotes)
    
        try 
            Sequencer sequencer = MidiSystem.getSequencer();
            sequencer.open();
            Sequence sequence = new Sequence(Sequence.PPQ, 4);
            Track track = sequence.createTrack();

            for (int i = 0; i < numOfNotes; i++)
            
                track.add(makeEvent(144, 1, i+48, 100, i));
                track.add(makeEvent(128, 1, i+48, 100, i + 2));
            

            sequencer.setSequence(sequence);
            sequencer.setTempoInBPM(88);
            System.out.println("Playing (length=" + sequencer.getMicrosecondLength()/1000000f + "s)...");
            sequencer.start();

            while (true) 
                // Never returns false, so the program never quits
                if (!sequencer.isRunning()) 
                    sequencer.close();
                    System.exit(1);
                
            
        
        catch (Exception ex) 
            ex.printStackTrace();
        
    

    public MidiEvent makeEvent(int command, int channel, int note, int velocity, int tick)
    
        MidiEvent event = null;
        try 
            ShortMessage a = new ShortMessage();
            a.setMessage(command, channel, note, velocity);
            event = new MidiEvent(a, tick);
        
        catch (Exception ex) 
            ex.printStackTrace();
        
        return event;
    

【参考方案1】：

我打算删除它，但我会保留它并发布答案。看来您需要在while 循环中调用sequencer.getMicrosecondPosition()。大概这会更新序列器类中的一些变量，然后当位置与getMicrosecondLength 返回的值匹配时，使isRunning 正确返回false。

具体来说：

while (true) 
    if (!sequencer.isRunning()) 
        sequencer.close();
        System.exit(1);
    
    sequencer.getMicrosecondPosition();