如何检测音量的上下按下

@Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
    switch (keyCode) {
        case KeyEvent.KEYCODE_VOLUME_CHANGED:
            // 音量键被按下
            return true;
        default:
            return super.onKeyDown(keyCode, event);
    }
}

NotificationCenter.default.addObserver(self, selector: #selector(volumeChanged(_:)), name: Notification.Name(rawValue: "AVSystemController_SystemVolumeDidChangeNotification"), object: nil)

@objc func volumeChanged(_ notification: Notification) {
    // 音量发生变化
}

private void Form1_KeyDown(object sender, KeyEventArgs e)
{
    if (e.KeyCode == Keys.VolumeDown || e.KeyCode == Keys.VolumeUp)
    {
        // 音量键被按下
    }
}

window.addEventListener('volumechange', function() {
    // 浏览器音量发生变化
});