Android rear camera not found when XR->Cardboard enabled

I'm attempting to add functionality to my app to allow the user to "peek" at the real world using the phone's rear camera (Android phone, cardboard-type non-Daydream headpiece).

I followed N3K EN's tutorial (embedded at bottom of post) and it worked perfectly (code below)... until I went into PlayerSettings->XR Settings, checked "Virtual Reality Supported", and added "Cardboard" as a Virtual Reality SDK. When I ran it after making the change, no cameras were found.

What do I have to do differently to allow the camera to work when the phone is running as a CardboardVR device?

If it matters, the phone in question is a Nexus 6P (rooted, Android 8.1.0), and I'm running Unity 2018.2.11f1.

Code (CSharp):

1. using System.Collections;
2. using System.Collections.Generic;
3. using UnityEngine;
4. using UnityEngine.UI;
5.  
6. public class PhoneCamera : MonoBehaviour {
7.  
8.     private bool camAvailable = false;
9.     private WebCamTexture backCam;
10.     private Texture defaultBackground;
11.  
12.     public RawImage background;
13.     public AspectRatioFitter fit;
14.  
15.     // Use this for initialization
16.     void Start () {
17.         defaultBackground = background.texture;
18.         WebCamDevice[] devices = WebCamTexture.devices;
19.         if (devices.Length == 0) {
20.             Debug.Log("no camera detected");
21.             return;
22.         }
23.         for (int x=0; x < devices.Length; x++) {
24.             if (devices[x].isFrontFacing == false) {
25.                 backCam = new WebCamTexture(devices[x].name, Screen.width, Screen.height);
26.                 break;
27.             }
28.         }
29.         if (backCam == null) {
30.             Debug.Log("no rear-facing camera detected");
31.             return;
32.         }
33.         backCam.Play();
34.         background.texture = backCam;
35.         camAvailable = true;
36.     }
37.  
38.     // Update is called once per frame
39.     void Update () {
40.         if (!camAvailable)
41.             return;
42.  
43.         float ratio = (float)backCam.width / (float)backCam.height;
44.         fit.aspectRatio = ratio;
45.         float scaleY = backCam.videoVerticallyMirrored ? -1f : 1f;
46.         background.rectTransform.localScale = new Vector3(1f, scaleY, 1f);
47.         int orient = -backCam.videoRotationAngle;
48.         background.rectTransform.localEulerAngles = new Vector3(0, 0, orient);
49.  
50.     }
51. }

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That's a good question. Probably not. I remember seeing Unity Player ask for permission (and be granted it) automatically when I ran it without VR, and just kind of took for granted that if Unity did it for non-VR Android apps, it would do it automatically for VR, too.

Where do I need to look, and what do I need to explicitly set?

 

Hmmm... now I'm officially confused.

According to the page about Android permissions in Unity's documentation...

1. Unity automatically declares the permissions for Camera if something uses WebCamTexture, HOWEVER...
2. Further down the same page, it says that Unity doesn't support API23+ ("Android 6.0/Marshmallow") runtime permissions.

Which is weird, because I was asked to grant camera permission the first time I ran it (but before I enabled XR with Cardboard). It almost looks like Unity quietly implemented runtime permissions for non-XR without updating the docs, but not for XR-using apps.