// 1开启距离感应功能
[UIDevice currentDevice].proximityMonitoringEnabled = YES;
// 2监听距离感应的通知
[[NSNotificationCenter defaultCenter] addObserver:self
selector:@selector(proximityChange:)
name:UIDeviceProximityStateDidChangeNotification
object:nil];

• (void)proximityChange:(NSNotificationCenter *)notification {
  if ([UIDevice currentDevice].proximityState == YES) {
  NSLog(@"某个物体靠近了设备屏幕"); // 屏幕会自动锁住
  } else {
  NSLog(@"某个物体远离了设备屏幕"); // 屏幕会自动解锁
  }
  }