如何在Java中实时读取MIDI输入流

import javax.sound.midi.MidiMessage;
import javax.sound.midi.Receiver;
import javax.sound.midi.ShortMessage;

public class MyMidiReceiver implements Receiver {

    @Override
    public void send(MidiMessage message, long timeStamp) {
        // 检查消息类型，通常我们关心ShortMessage
        if (message instanceof ShortMessage shortMessage) {
            // 获取MIDI命令（例如，Note ON, Note OFF, Control Change等）
            int command = shortMessage.getCommand();
            // 获取MIDI通道
            int channel = shortMessage.getChannel();
            // 获取第一个数据字节（例如，音符编号或控制器编号）
            int data1 = shortMessage.getData1();
            // 获取第二个数据字节（例如，力度或控制器值）
            int data2 = shortMessage.getData2();

            // 处理Note ON事件
            if (command == ShortMessage.NOTE_ON) {
                // 过滤掉力度为0的Note ON，这通常表示Note OFF
                if (data2 > 0) {
                    System.out.println("Note ON: Note=" + data1 + ", Velocity=" + data2 + ", Channel=" + channel + ", Time=" + timeStamp);
                    // 在这里执行你的实时逻辑，例如更新乐谱显示、触发声音等
                    // 注意：长时间运行的任务应在新线程中执行，以避免阻塞MIDI事件流
                } else {
                    // 处理力度为0的Note ON作为Note OFF
                    System.out.println("Note OFF (Velocity 0): Note=" + data1 + ", Channel=" + channel + ", Time=" + timeStamp);
                }
            }
            // 处理Note OFF事件
            else if (command == ShortMessage.NOTE_OFF) {
                System.out.println("Note OFF: Note=" + data1 + ", Velocity=" + data2 + ", Channel=" + channel + ", Time=" + timeStamp);
            }
            // 处理控制改变事件
            else if (command == ShortMessage.CONTROL_CHANGE) {
                System.out.println("Control Change: Controller=" + data1 + ", Value=" + data2 + ", Channel=" + channel + ", Time=" + timeStamp);
            }
            // 可以根据需要添加其他MIDI消息类型的处理
        }
    }

    @Override
    public void close() {
        System.out.println("MIDI Receiver closed.");
        // 清理资源（如果需要）
    }
}

import javax.sound.midi.MidiDevice;
import javax.sound.midi.MidiSystem;
import javax.sound.midi.Sequence;
import javax.sound.midi.Sequencer;
import javax.sound.midi.Transmitter;
import java.io.File;
import java.io.IOException;
import java.util.concurrent.TimeUnit;

public class MidiInputRecorderAndProcessor {

    public static void main(String[] args) throws Exception {
        // 1. 列出所有MIDI设备并选择输入设备
        MidiDevice.Info[] infos = MidiSystem.getMidiDeviceInfo();
        MidiDevice inputDevice = null;

        System.out.println("Available MIDI Devices:");
        for (int i = 0; i < infos.length; i++) {
            System.out.println(i + ": " + infos[i].getName() + " - " + infos[i].getDescription());
            // 简单示例：选择第一个包含"USB"或"MIDI"的设备作为输入
            // 实际应用中应提供用户选择或更智能的匹配
            if (inputDevice == null && (infos[i].getName().contains("USB") || infos[i].getName().contains("MIDI"))) {
                try {
                    MidiDevice device = MidiSystem.getMidiDevice(infos[i]);
                    if (device.getMaxTransmitters() != 0) { // 确保是输入设备
                        inputDevice = device;
                        System.out.println("Selected Input Device: " + infos[i].getName());
                    }
                } catch (Exception e) {
                    // 忽略无法打开的设备
                }
            }
        }

        if (inputDevice == null) {
            System.err.println("No suitable MIDI input device found.");
            return;
        }

        // 2. 打开输入设备
        inputDevice.open();

        // 3. 设置实时处理器 (自定义Receiver)
        Transmitter realTimeTransmitter = inputDevice.getTransmitter();
        MyMidiReceiver myReceiver = new MyMidiReceiver();
        realTimeTransmitter.setReceiver(myReceiver);
        System.out.println("Real-time MIDI processing started.");

        // 4. 设置Sequencer进行录制
        Sequencer sequencer = MidiSystem.getSequencer();
        sequencer.open();

        // 创建一个空的Sequence用于录制
        Sequence sequence = new Sequence(Sequence.PPQ, 24);
        sequencer.setSequence(sequence);
        sequencer.recordEnable(sequence.createTrack(), -1); // 录制到新轨道

        // 获取第二个Transmitter连接到Sequencer的Receiver
        // 注意：某些设备可能只提供一个Transmitter，需要检查getMaxTransmitters()
        Transmitter recordingTransmitter = inputDevice.getTransmitter(); 
        recordingTransmitter.setReceiver(sequencer.getReceiver());
        System.out.println("MIDI recording to Sequencer started.");

        sequencer.startRecording();

        // 5. 运行一段时间后停止并保存
        System.out.println("Listening and recording for 10 seconds...");
        TimeUnit.SECONDS.sleep(10); // 模拟运行10秒

        sequencer.stopRecording();
        System.out.println("Recording stopped.");

        // 6. 保存录制的MIDI文件
        try {
            File midiFile = new File("recorded_midi.mid");
            MidiSystem.write(sequence, 0, midiFile);
            System.out.println("MIDI sequence saved to " + midiFile.getAbsolutePath());
        } catch (IOException e) {
            System.err.println("Error saving MIDI file: " + e.getMessage());
        }

        // 7. 关闭资源
        myReceiver.close();
        realTimeTransmitter.close();
        recordingTransmitter.close();
        sequencer.close();
        inputDevice.close();
        System.out.println("All MIDI resources closed.");
    }
}