[[UIDevice currentDevice] setProximityMonitoringEnabled:YES];
  [[NSNotificationCenter defaultCenter] addObserver:self
                                           selector:@selector(sensorStateChange:)
                                               name:@"UIDeviceProximityStateDidChangeNotification"
                                             object:nil];

-(void)sensorStateChange:(NSNotificationCenter *)notification;
{
  if ([[UIDevice currentDevice] proximityState] == YES) {
      NSLog(@"屏幕熄滅");
  }else{
      NSLog(@"屏幕亮起");
  }
}