[solved] Unable to use callbacks in unity?

Unity
1

I’m working on a game completely consisting of sounds in unity, and I want to make use of FMOD’s callback system to identify things like music end, and beat markers, the problem is that I am completely unable to do anything from inside the callback in unity. I’ve done a lot of things to try to work around any thread shenanigans that might be happening; One of it was to simply store that the callback actually happened and doing the hard work later, in a MonoBehaviour’s update

private FMOD.RESULT Stopped(EVENT_CALLBACK_TYPE type, EventInstance eventInstance, IntPtr parameters)
{
try
{
var test = this == null;
_callbackHappened = true;
}
catch (Exception e)
{
var message = e.Message;
}

    return FMOD.RESULT.OK;

}

What is happening is that the test bool is sometimes returning true, and the _callbackHappened assignment throws a nullreference exception…
Could I be wrong or using callbacks on unity isn’t supported?

2

Callbacks require the use of explicitly pinning memory so that the memory isn’t freed by the garbage collector.

We have an example on our website of how to use callbacks:
https://fmod.com/resources/documentation-api?page=content/generated/engine_new_unity/script_example_timeline.html#/

1 Like
3

Why are callbacks so tedious? The function headers and extra library calls going on here are quite dizzying. Are there any pitfalls to lookout for when making callbacks a commonplace in our games?

2 Likes
4

That really did the trick! It sure wasn’t as painless as I want it t be, but after encapsulating all that dizzy stuff it became really simple to work with.
Thanks for the quick response.

5

@Tanner The extra work is required when interfacing with native code (C, C++, Objective-C, etc.). https://docs.unity3d.com/Manual/NativePlugins.html

As Rafael mentioned, the hard part is the initial setup.

6

@Cameron - I got it working in my game as well this evening. I actually am attaching and removing the callbacks to/from my event in real-time as the game plays out. There doesn’t seem to be an option to delete a callback from an event once you attach it, so I am just swapping it out for an empty callback before I free the original data object the callback was writing to.

7

Only one problem though is that destroying the object as mentioned on the example while an event is playing freezes my unity editor

8

I believe the fix for that will be the same as posted here:

It is due to the GCHandle being freed before the callback is actually finished with it.