距离传感器

- (void)viewDidLoad {
    [super viewDidLoad];
    
    // 距离传感器默认是关闭(实时的检测是否有物品靠近,所有非常耗电)
    // [UIApplication sharedApplication].proximitySensingEnabled
    [UIDevice currentDevice].proximityMonitoringEnabled = YES;
    
    // 通过通知(一旦有物品靠近或者离开的时候,都会发出通知)
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(proximityStateDidChange) name:UIDeviceProximityStateDidChangeNotification object:nil];
}
// 当有物品靠近或者离开的时候会调用该方法
- (void)proximityStateDidChange{
    if ([UIDevice currentDevice].proximityState) {
        NSLog(@"有物品靠近");
    } else {
        NSLog(@"有物品离开");
    }
}
- (void)dealloc{
    [[NSNotificationCenter defaultCenter] removeObserver:self];
}