Proximity sensor in landscape

I'm developing an app for virtual headset (cardboard).

I want to detect when iphone has been enclosed in the cardboard by using the proximity sensor.

Problems:

• once [[UIDevice currentDevice] proximityState] == YES the screen goes black, while I need to show images.
• the proximity notification is generated only in portrait mode. I need it (only) in landscape mode.

Here my code:

- (void)viewDidLoad {
    [super viewDidLoad];
    [[UIDevice currentDevice] setProximityMonitoringEnabled:YES];
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(proxSensorStateMonitor:)
                                                 name:UIDeviceProximityStateDidChangeNotification object:nil];
    [[UIApplication sharedApplication] setIdleTimerDisabled:YES];
}


- (void)proxSensorStateMonitor:(NSNotificationCenter *)notification {
    if ([[UIDevice currentDevice] proximityState] == YES) {
        [[UIDevice currentDevice] setProximityMonitoringEnabled:NO];
          // Provide content for Cardboard
    }
}