MissingGlContextException when opening another screen from AR

I’m not sure if my code will work in all cases, so I’d need to make much more testing before making a PR. I can’t promise that I’ll be able to do it any time soon but I’ll try. My application has a single screen with AR, so I just save the EGL context using static variables. It might or might not work for more complex apps. Below I provide the whole code that I used for my work-around:

When ArSceneView is created or resumed:

    private fun restoreEglContext() {
        if (Looper.getMainLooper().thread != Thread.currentThread()) {
            throw IllegalStateException("restoreEglContext called from non-UI thread")
        }
        debugLog("Restoring EGL context")
        if (savedContext != null && savedContext != EGL14.EGL_NO_CONTEXT) {
            if (!EGL14.eglMakeCurrent(savedDisplay, savedDrawSurface, savedReadSurface, savedContext)) {
                debugLog("Failed to restore")
            }
        } else {
            debugLog("Nothing to restore")
        }
    }

When ArSceneView is paused:

    private fun saveEglContext() {
        if (Looper.getMainLooper().thread != Thread.currentThread()) {
            throw IllegalStateException("saveEglContext called from non-UI thread")
        }
        debugLog("Saving EGL context")
        val currentContext = EGL14.eglGetCurrentContext()
        if (currentContext == null || currentContext == EGL14.EGL_NO_CONTEXT) {
            debugLog("Nothing to save")
        } else {
            savedContext = currentContext
            savedDisplay = EGL14.eglGetCurrentDisplay()
            savedDrawSurface = EGL14.eglGetCurrentSurface(EGL14.EGL_DRAW)
            savedReadSurface = EGL14.eglGetCurrentSurface(EGL14.EGL_READ)
            EGL14.eglMakeCurrent(
                savedDisplay,
                EGL14.EGL_NO_SURFACE,
                EGL14.EGL_NO_SURFACE,
                EGL14.EGL_NO_CONTEXT
            )
        }
    }

When ArSceneView is destoyed:

arSceneView?.renderer?.dispose()

Static variables to store the context:

    companion object {
        private var savedContext: EGLContext? = null
        private var savedDisplay: EGLDisplay? = null
        private var savedReadSurface: EGLSurface? = null
        private var savedDrawSurface: EGLSurface? = null
    }

EDIT: I actually don’t know if the approach in my work-around is something that should be used in the library. Probably the EGL14.eglMakeCurrent should be called internally for every frame.

After a long night of debugging my colleagues created a work-around for the problem in our app. The reason of the problem is that there’s the assumption in Sceneform that nothing will touch the singleton EGL context. Unfortunately, some code used by the Stripe library cleared the singleton. The work-around is to save the EGL context every time the activity is paused and restore it every time it’s resumed. Saving can be done by storing the value of EGL14.eglGetCurrentContext() and then setting the singleton context to EGL14.EGL_NO_CONTEXT using EGL14.eglMakeCurrent. Restoring can be done with the EGL14.eglMakeCurrent call. There’s also one other problem with Sceneform: the method ArSceneView.destroy() doesn’t call renderer?.dispose(), so it has to be called manually every time the ArSceneView.destroy() is called.