Java :将MIDI键盘连接到默认合成器

Question

我有个MIDI键盘。我想要的只是一个例子，说明我如何设置默认的软件合成器来播放声音，就像我玩键盘一样。

package cleffsgame;

import java.util.logging.Level;
import java.util.logging.Logger;
import javax.sound.midi.MidiDevice;
import javax.sound.midi.MidiSystem;
import javax.sound.midi.MidiUnavailableException;

public class CheckDevices {

    public static void main(String[] args) {
        MidiDevice device;
        // display each device's properties
        for (MidiDevice.Info info: MidiSystem.getMidiDeviceInfo()) {

            try {
                device = MidiSystem.getMidiDevice(info);

                System.out.println("\nDevice: ");
                System.out.println("Name: " + device.getDeviceInfo().getName());
                System.out.println("Vendor: " + device.getDeviceInfo().getVendor());
                System.out.println("Version: " + device.getDeviceInfo().getVersion());
                System.out.println("Description: " + device.getDeviceInfo().getDescription());
                System.out.println("Transmitters: " + device.getMaxTransmitters());
                System.out.println("Receivers: " + device.getMaxReceivers());

            } catch (MidiUnavailableException ex) {
                Logger.getLogger(CheckDevices.class.getName()).log(Level.SEVERE, null, ex);
            }
        }
    }
}

通过运行上面的代码，我得到了以下输出：

跑： 设备名称: Gervill Vendor: OpenJDK版本: 1.0描述:软件MIDI合成器发射机:0接收器：-1 设备名称:氧气49供应商:m-音频版本:未知版本描述:氧气49发射机：-1接收器:0 设备名称:氧气49供应商:m-音频版本:未知版本描述:氧气49发射机:0接收器：-1 设备名称:实时Sequencer : Oracle公司版本: 1.0版本:软件顺序发射器：-1接收器：-1成功构建(总时间:2秒)

但是当我运行下面的代码时，当我按下键时，没有声音被播放。

package cleffsgame;

import java.util.logging.Level;
import java.util.logging.Logger;
import javax.sound.midi.MidiDevice;
import javax.sound.midi.MidiSystem;
import javax.sound.midi.MidiUnavailableException;
import javax.sound.midi.Receiver;
import javax.sound.midi.Synthesizer;
import javax.sound.midi.Transmitter;

/**
 *
 * @author umberto
 */
public class Test {

    public static void main(String[] args) {
        MidiDevice inputDevice = null, synthDevice = null;
        Transmitter transmitter = null;
        Synthesizer synthesizer = null;
        Receiver receiver = null;

        try {
            inputDevice = MidiSystem.getMidiDevice(MidiSystem.getMidiDeviceInfo()[1]);
            synthDevice = MidiSystem.getMidiDevice(MidiSystem.getMidiDeviceInfo()[0]);

        } catch (MidiUnavailableException ex) {
            Logger.getLogger(Test.class.getName()).log(Level.SEVERE, null, ex);
        }

        // goodDevice must be Oxygen 49 transmitter (MIDI Input)
        if (inputDevice != null && synthDevice != null) {
            try {
                transmitter = inputDevice.getTransmitter();
                System.out.println("Transmitter: " + inputDevice.getDeviceInfo());
                System.out.println(String.format("T/R: %s/%s", inputDevice.getMaxTransmitters(), inputDevice.getMaxReceivers()));

                receiver = synthDevice.getReceiver();
                System.out.println("Receiver: " + synthDevice.getDeviceInfo());
                System.out.println(String.format("T/R: %s/%s", synthDevice.getMaxTransmitters(), synthDevice.getMaxReceivers()));

                transmitter.setReceiver(receiver);
                System.out.println("GoodDevice is open... check sound\n");
                inputDevice.open();
                synthDevice.open();

            } catch (Exception ex) {
                Logger.getLogger(Test.class.getName()).log(Level.SEVERE, null, ex);
            }
        }

    }


}

似乎有更多的工作要做，而不是像我从docs Synthesizer.receiver中获得的那样，将一个InputDevice.transmitter连接到一个https://docs.oracle.com/javase/tutorial/sound/MIDI-synth.html。

Answer 1

这个对我有用

transmitter.setReceiver(new Receiver() {
    @Override
    public void send(MidiMessage message, long timeStamp) {
        receiver.send(message, -1);
    }
    @Override
    public void close() {
        receiver.close();
    }
});

Answer 2

在获得发射机/接收器之前打开设备可能是个好主意。

但实际的问题是，这个程序会立即退出，因此设备不会在有效的时间内打开。

Answer 3

最近也想做同样的事。Java教程和堆栈溢出的答案不起作用。问题是，我把timestamp上的键盘注释传递给内部合成器。修复方法是将-1作为时间戳传递。

本例使用Kotlin调用。

JDK 17，MacOS 11.3，Kotlin 1.6

import javax.sound.midi.*

class ReceiverAdapter (val targetReceiver: Receiver) : Receiver {

    override fun send(midiMsg: MidiMessage, timeStamp: Long) {
        targetReceiver.send(midiMsg, -1); // only works for me when i pass -1 as timestamp instead of original value from keyboard
    }
    override fun close() {  }
}

class MidiKeyboardInternalSynthExample {

    companion object {

        fun doIt(keyboardDeviceName: String){

            // connect external keyboard to internal synth
            val midiTransmitter = find1stMidiTransmitterWithName(keyboardDeviceName)
            if(midiTransmitter != null) {
                val synth = MidiSystem.getSynthesizer()!!
                val midiReceiver = ReceiverAdapter(synth.receiver)
                midiTransmitter.transmitter.receiver = midiReceiver
                synth.open()
                midiTransmitter.open()
            }
            else {
                println("Didn't find MIDI transmitter named '$keyboardDeviceName'.")
            }
        }

        fun find1stMidiTransmitterWithName(deviceName: String): MidiDevice? =
            MidiSystem.getMidiDeviceInfo()
                ?.filter { info -> info.name == deviceName }
                ?.map { info -> MidiSystem.getMidiDevice(info) }
                ?.filter { device -> device.maxTransmitters == -1 }
                ?.first()
    }
}

fun main(args: Array<String>) {
    MidiKeyboardInternalSynthExample.doIt("LPK25")
}