Asus Nexus 7 2013 camera.open 连接相机服务失败

Question

我只在 Asus Nexus 7 2013 上遇到问题。所有其他设备，包括 Asus Nexus 7 2012 都可以正常工作。
此设备有 2 个摄像头 ID：0、1。
但是我无法打开相机，同时使用它们。

//...
try {
     //cameraID: 0 or 1
     camera = Camera.open(cameraID);
     //...
} catch (Exception e) {
     e.printStackTrace();
}

所以我得到：

java.lang.RuntimeException: Fail to connect to camera service
android.hardware.Camera.<init>(Camera.java:495)
android.hardware.Camera.open(Camera.java:341)

Answer 1

问题出在新的 Android 6+ 功能中：在运行时请求权限。

if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.M) {
    if (!permissionRequestInProgress) {
          permissionRequestInProgress = true;
              new Handler().post(new Runnable() {
                  @Override
                  public void run() {
                      if (ContextCompat.checkSelfPermission(RootActivity.this, Manifest.permission.CAMERA)
                              != PackageManager.PERMISSION_GRANTED)
                      {
                          ActivityCompat.requestPermissions(RootActivity.this,
                                        new String[]{Manifest.permission.CAMERA},
                                        CAMERA_PERMISSION_REQUEST);
                      } else {
                          //we got it
                      }
              }
           });
    }
}

---

@Override
public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults) {
    switch (requestCode) {
        case CAMERA_PERMISSION_REQUEST:
            if (grantResults.length > 0
                    && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                // permission was granted
                //we got it
            } else {
                // permission denied
            }
            permissionRequestInProgress = false;
            break;
        default:
            super.onRequestPermissionsResult(requestCode, permissions, grantResults);
    }
}