Bug Unable to get OpenGL context from the Java side on Android

As per the tittle, I am unable to get the EGL14.eglGetCurrentContext() inside an Android Java class. More precisely, the returned context is equal to EGL14.EGL_NO_CONTEXT. My interpretation is that the code is called from the main Unity thread yet the code is not able to get the OpenGL context. Multithreaded rendering is disabled. The project is a Unity project exported to Android. This C# code calls the Java initSurface method from an Update function of a MonoBehavior:

Code (CSharp):

1. private void Update()
2.     {
3.         if (_camMonitorInstance == null)
4.         {
5.             // it is important to call this in update method. Single Threaded Rendering will run in UnityMain Thread
6.             InitAndroidSurface(camWidth, camHeight);
7.         }
8.         else
9.         {
10.             _camMonitorInstance.Call("updateSurfaceTexture");
11.         }
12.     }

This should ensure that it will be called from the UnityMain thread. I am very confident that the thread is UnityMain because in updateSurfaceTexture Thread.currentThread().getName().equals("UnityMain") is true.

Code (Java):

1. private void initSurface() {
2.         unityContext = EGL14.eglGetCurrentContext();
3.         unityDisplay = EGL14.eglGetCurrentDisplay();
4.         unityDrawSurface = EGL14.eglGetCurrentSurface(EGL14.EGL_DRAW);
5.         unityReadSurface = EGL14.eglGetCurrentSurface(EGL14.EGL_READ);
6.  
7.         if (unityContext == EGL14.EGL_NO_CONTEXT) {
8.             Log.e(TAG, "UnityEGLContext is invalid -> Most probably wrong thread");
9.         }
10.  
11.         EGL14.eglMakeCurrent(unityDisplay, unityDrawSurface, unityReadSurface, unityContext);
12.  
13.         GLES20.glActiveTexture(GLES20.GL_TEXTURE0);
14.         GLES20.glBindTexture(GLES11Ext.GL_TEXTURE_EXTERNAL_OES, _unityTextureId);
15.         GLES20.glTexParameterf(GLES11Ext.GL_TEXTURE_EXTERNAL_OES, GLES20.GL_TEXTURE_MIN_FILTER, GLES20.GL_LINEAR);
16.         GLES20.glTexParameterf(GLES11Ext.GL_TEXTURE_EXTERNAL_OES, GLES20.GL_TEXTURE_MAG_FILTER, GLES20.GL_LINEAR);
17.         GLES20.glTexParameterf(GLES11Ext.GL_TEXTURE_EXTERNAL_OES, GLES20.GL_TEXTURE_WRAP_S, GLES20.GL_CLAMP_TO_EDGE);
18.         GLES20.glTexParameterf(GLES11Ext.GL_TEXTURE_EXTERNAL_OES, GLES20.GL_TEXTURE_WRAP_T, GLES20.GL_CLAMP_TO_EDGE);
19.         _surfaceTexture = new SurfaceTexture(_unityTextureId);
20.         _surfaceTexture.setDefaultBufferSize(_textureWidth, _textureHeight);
21.         _surface = new Surface(_surfaceTexture);
22.         _surfaceTexture.setOnFrameAvailableListener(this);
23.     }

 

This attempt is based on https://medium.com/xrpractices/external-texture-rendering-with-unity-and-android-b844bb7a35da. As you can see, the author has everything working whereas everyone is not able to get the OpenGL context. Also, everything seems to work on emulators but not on real devices.