Native plugin JNI issue when Multithreaded Rendering enabled

Unity Engine
,
1

Hi,
I come to make a post to ask for your help after 2 days’ trouble shooting.

My app would run in Android. I have a native plugin (attached). in C# script, I call functions with GL.IssuePluginEvent, and I also use DLL import some of it’s functions. And this plugin also do some JNI calls to android java libs like below:

SurfaceTexture::SurfaceTexture( JNIEnv * jni_ ) :
textureId( 0 ),
javaObject( NULL ),
jni( NULL ),
nanoTimeStamp( 0 ),
updateTexImageMethodId( NULL ),
getTimestampMethodId( NULL ),
setDefaultBufferSizeMethodId( NULL ),
setNotifyFrameAvailableMethodId( NULL )
{
static const char * className = “android/graphics/SurfaceTexture”; /// I would change this class later.
const jclass surfaceTextureClass = jni->FindClass(className);
if ( surfaceTextureClass == 0 ) {
FAIL( “FindClass( %s ) failed”, className );
}

you can see that the android class “android/graphics/SurfaceTexture” is the one to be load by JNI.

So the C# call the native plugin, and the native plugin can call java, and it also works well even when “Multithreaded Rendering” is enabled.

However, when I tried to load a customized java lib in this Native plugin (means, in plugin I do the call to a jar lib I write by myself, and put it to the Asset/Plugin/Android directory), issue happens when Multithreaded Rendering is enabled, the error is “FindClass xxx failed”. And the issue would not happen when Multithreaded Rendering is not enabled. I really have not idea why this happen.

So I got result, when Multithreaded Rendering is enabled, the native plugin can only call the System librarys (the above java class is a standard android class), not cannot call user’s customized java lib. is that right ? Can you share more about Multithreaded Rendering in Unity? In which level does the multi threads exist

Could you help on this, thanks a lot.

2681322–189479–Src.rar (7.66 KB)

2

the sample code in C# calling the plugin is as below:

class Test : MonoBehaviour
{
#if (UNITY_ANDROID && !UNITY_EDITOR)
[DllImport(“OculusMediaSurface”)]
private static extern void OVR_Media_Surface_Init();

[DllImport(“OculusMediaSurface”)]
protected static extern IntPtr OVR_Media_Surface(IntPtr surfaceTexId, int surfaceWidth, int surfaceHeight, int screenWidth, int screenHeight);

[DllImport(“OculusMediaSurface”)]
private static extern void OVR_Media_Surface_SetEventBase(int eventBase);

#endif

public void Awake()
{
#if UNITY_ANDROID && !UNITY_EDITOR
OVR_Media_Surface_Init();
IssuePluginEvent(MediaSurfaceEventType.Initialize);
#endif
}
private static void IssuePluginEvent(MediaSurfaceEventType eventType)
{
GL.IssuePluginEvent((int)eventType + EventBase);
}
private enum MediaSurfaceEventType
{
Initialize = 0,
Shutdown = 1,
Check = 2, // just trigger surfaceTexture.update (for onFrameAvailable) without actual texture update
Update = 3, // trigger surfaceTexture.update and update texture
SkipFirstFrame = 4,
Max_EventType
};
///


/// The start of the numeric range used by event IDs.
///
///
/// If multiple native rundering plugins are in use, the Oculus Media Surface plugin’s event IDs
/// can be re-mapped to avoid conflicts.
///
/// Set this value so that it is higher than the highest event ID number used by your plugin.
/// Oculus Media Surface plugin event IDs start at eventBase and end at eventBase plus the highest
/// value in MediaSurfaceEventType.
///
public static int EventBase
{
get { return mEventBase; }
set
{
mEventBase = value;
#if (UNITY_ANDROID && !UNITY_EDITOR)
OVR_Media_Surface_SetEventBase(mEventBase);
#endif
}
}
private static int mEventBase = 0;
}

3

Not that I’m completely sure of this, but perhaps you need to attach your jni env pointer to the current thread before using it to find classes.

4

yes, the jni env pointer is attached to the thread already before the call. it works well when Multithreaded Rendering is enabled.

5

This might be helpful.