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final SensorManager sensorManager 
        = (SensorManager)getSystemService(Context.SENSOR_SERVICE);
        final Sensor lightSensor 
        = sensorManager.getDefaultSensor(Sensor.TYPE_LIGHT);

sensorManager.registerListener(lightSensorEventListener, 
                    lightSensor, 
                    SensorManager.SENSOR_DELAY_FASTEST);

@Override
  public void onSensorChanged(SensorEvent event) {
   // TODO Auto-generated method stub
   if(event.sensor.getType()==Sensor.TYPE_LIGHT){
    currentReading = event.values[0];
    Log.d("light", Float.toString(currentReading));
     }
  }