Common problems

StartCoroutine can only be called from the main thread in Unity

Sometimes you want to start Unity coroutine in a handler of the EventReceived event of InputDevice. Your code can be executed on a separate thread in this case. It can happen because events are received by device on a separate (system) thread.

But UI related things like call of StartCoroutine can be executed on UI thread only. You can use the solution from here: https://stackoverflow.com/a/56715254.

Related question on StackOverflow: Catching and processing multiple keyboard inputs at once

InputDevice declared as a local variable

If an instance of the InputDevice is declared as a local variable and you’ve subscribed to its EventReceived event, the event handler won’t be called or you can get undefined behavior. For example, let’s look at this code:

private void StartListening()
{
    var inputDevice = InputDevice.GetByName("My Device");
    inputDevice.EventReceived += OnEventReceived;
    inputDevice.StartEventsListening();
}

private void OnEventReceived(object sender, MidiEventReceivedEventArgs e)
{
    // Do something ...
}

What happens when the StartListening method exits? Right, all local variables are marked as ready for garbage collection, so they will be deleted within a short time span. So the OnEventReceived method becomes attached to a deleted entity (inputDevice) when the StartListening exited. In the best case you just won't get OnEventReceived called. In worst case you may get different strange things, see this issues:

• InputDevice event listening crash
• Crash when running in Unity on M2 MacBook

Input device must be stored in a class field:

private InputDevice _inputDevice;

private void StartListening()
{
    _inputDevice = InputDevice.GetByName("My Device");
    _inputDevice.EventReceived += OnEventReceived;
    _inputDevice.StartEventsListening();
}

And don't forget to dispose of the device when you're done with it. Please read the Input device article to learn more.