使用iOS中的传感器检测面朝上的位置

- (void)viewDidLoad {
   [[UIDevice currentDevice] beginGeneratingDeviceOrientationNotifications];
   [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(orientationChanged:) name:UIDeviceOrientationDidChangeNotification object:[UIDevice currentDevice]];
}


- (void)orientationChanged:(NSNotification *)note{
   UIDevice * device = note.object;
   //  NSLog(@"rotation main %d ",device.orientation;);

  switch(device.orientation){
    case 1:
        //Portrait
    break;

    case 4:
       //landscape right
    break;

    case 3:
        //landscape left
    break;

    default:
        //other orientations
    break;
   };
}

我用定时定时器解决了这个问题。每0.5秒调用下面的方法并工作。

- (void)viewDidLoad {
    [super viewDidLoad];

    theQueue = [[NSOperationQueue alloc] init];

    returnedData = [[CMAccelerometerData alloc] init];
    motionManager = [[CMMotionManager alloc] init];
    [NSTimer scheduledTimerWithTimeInterval:0.5f
                                     target:self selector:@selector(checkPhonePosition:) userInfo:nil repeats:YES];

}


-(void)checkPhonePosition:(NSTimer *)timer {


    [motionManager startAccelerometerUpdatesToQueue:theQueue withHandler:^(CMAccelerometerData *accelerometerData, NSError *error) {

        returnedData = motionManager.accelerometerData;

        z = returnedData.acceleration.z;

        NSLog(@"Z: %f", z);


    }];

    if(z > -1.0 && z < -0.8 ){
        btnOpen.hidden = NO;
    }
    else{
        btnOpen.hidden = YES;
    }
}