Preview.SurfaceProvider

fun onSurfaceRequested(request: SurfaceRequest): Unit

class MyGlSurfaceProvider implements Preview.SurfaceProvider {
    // This executor must have also been used with Preview.setSurfaceProvider() to
    // ensure onSurfaceRequested() is called on our GL thread.
    Executor mGlExecutor;

    @Override
    public void onSurfaceRequested(@NonNull SurfaceRequest request) {
        // If our GL thread/context is shutting down. Signal we will not fulfill
        // the request.
        if (isShuttingDown()) {
            request.willNotProvideSurface();
            return;
        }

        // Create the surface and attempt to provide it to the camera.
        Surface surface = resetGlInputSurface(request.getResolution());

        // Provide the surface and wait for the result to clean up the surface.
        request.provideSurface(surface, mGlExecutor, (result) -> {
            // In all cases (even errors), we can clean up the state. As an
            // optimization, we could also optionally check for REQUEST_CANCELLED
            // since we may be able to reuse the surface on subsequent surface requests.
            closeGlInputSurface(surface);
        });
    }
}