gistfile1.m

// 添加通知
[[UIDevice currentDevice] setProximityMonitoringEnabled:YES];
    if ([UIDevice currentDevice].proximityMonitoringEnabled == YES)
        [[NSNotificationCenter defaultCenter] addObserver:self
                                             selector:@selector(proximitySensorChange:) 
                                                 name:UIDeviceProximityStateDidChangeNotification
                                               object:nil];

// 移除通知
if ([UIDevice currentDevice].proximityMonitoringEnabled == YES)
        [[NSNotificationCenter defaultCenter] removeObserver:self 
                                                    name:UIDeviceProximityStateDidChangeNotification
                                                  object:nil];
    [[UIDevice currentDevice] setProximityMonitoringEnabled:NO];