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我正在开发一个在线乐谱阅读培训师，这里有一个原型。我能够实现对以前连接的 MIDI 键盘的访问，但是，我正在努力实现热插拔场景。

我的最后一次拍摄是这样的：

    setupDevices(inputs){
    let deviceName = '';

    inputs.forEach((value, key, map) => {
        if (value.connection === 'open' || value.connection === 'pending' ){

            value.open().then((midiInput) => {
                console.log(`Opened ${midiInput.name}`);
                midiInput.onmidimessage = midiController.onMIDIMessage;
            }, null);
        } else {
            value.onmidimessage = null;
        }
    });

    if (deviceName.length === 0) {
        deviceName = 'none';
    }

    document.getElementById('connectedDevice').setAttribute('value', deviceName);
},

onMIDISuccess(midiAccess) {
    midiAccess.onstatechange = (evt) => {
        console.log('MIDI config changed');
        midiController.setupDevices(evt.currentTarget.inputs);
    };
}

在调试时，所有的 Promise 都会用好看的参数调用，但我无法接收到任何按键消息。此外，console.log( Opened ${midiInput.name}) 的调用次数也比预期的要多：

midiController.js:57 MIDI config changed
midiController.js:40 Opened KOMPLETE KONTROL - 1
midiController.js:57 MIDI config changed
midiController.js:40 Opened KOMPLETE KONTROL - 1
midiController.js:57 MIDI config changed
midiController.js:40 Opened KOMPLETE KONTROL - 1
midiController.js:40 Opened KOMPLETE KONTROL EXT - 1
midiController.js:40 Opened KOMPLETE KONTROL - 1
3
midiController.js:40 Opened KOMPLETE KONTROL EXT - 1
midiController.js:57 MIDI config changed
midiController.js:40 Opened KOMPLETE KONTROL - 1
midiController.js:40 Opened KOMPLETE KONTROL EXT - 1
midiController.js:57 MIDI config changed
midiController.js:40 Opened KOMPLETE KONTROL - 1
midiController.js:40 Opened KOMPLETE KONTROL EXT - 1
2
midiController.js:40 Opened Komplete Kontrol DAW - 1
midiController.js:57 MIDI config changed
midiController.js:40 Opened KOMPLETE KONTROL - 1
midiController.js:40 Opened KOMPLETE KONTROL EXT - 1
midiController.js:57 MIDI config changed
midiController.js:40 Opened KOMPLETE KONTROL - 1
midiController.js:40 Opened KOMPLETE KONTROL EXT - 1

 （所有这些都是在我刚刚打开控制器后打印出来的）。有什么提示吗？

4

1 回答 1

0 
function midiOnMIDImessage(event) {
        console.log(event);
    }
function requestMIDIAccessSuccess(midi) {
        var inputs = midi.inputs.values();
        for (var input = inputs.next(); input && !input.done; input = inputs.next()) {
            input.value.onmidimessage = midiOnMIDImessage;
        }
    }
navigator.requestMIDIAccess().then(requestMIDIAccessSuccess, requestMIDIAccessFailure);

请参阅工作示例

于 2018-08-30T06:06:15.100 回答