private void initializeARMode() {
 setInfoText("Switching to AR mode.");
 cleanupFragment(fragment);

 // Put the AR Fragment in the layout.
 fragment = new ArFragment();
 getSupportFragmentManager().beginTransaction()
         .replace(R.id.fragment_container, fragment)
         .commitAllowingStateLoss();

 // Add a listener that is called when the fragment is initialized and onResume is called
 // indicating the fragment is running.
 fragment.getLifecycle().addObserver(new LifecycleObserver() {
   @OnLifecycleEvent(Lifecycle.Event.ON_RESUME)
   public void connectListener() {
     ArFragment arFragment = (ArFragment) fragment;

     // Set the listener to handle user input.
     arFragment.setOnTapArPlaneListener(PolyGalleryActivity.this::onTapPlane);

     // Add the update listener, this is called every frame.
     Scene scene = arFragment.getArSceneView().getScene();
     scene.addOnUpdateListener(PolyGalleryActivity.this::onSceneUpdate);

     // Set the scene in the scene context helper object.
     sceneContext.setScene(scene);

     // Remove the lifecycle observer since we're all set up.
     fragment.getLifecycle().removeObserver(this);
   }
 });
}