title: How to read Heart rate from Android Wear
body: <p>I need to read the heart rate of the user at that instant. I tried using this code located in my main activity in the Wear project.</p>
  
  <pre>
  public class MainActivity extends WearableActivity implements SensorEventListener {
  
      private static final String TAG = "MainActivity";
      private TextView mTextViewHeart;
      SensorManager mSensorManager;
      Sensor mHeartRateSensor;
      SensorEventListener sensorEventListener;
  
      @Override
      protected void onCreate(Bundle savedInstanceState) {
          super.onCreate(savedInstanceState);
          setContentView(R.layout.activity_main);
  
          mTextViewHeart = (TextView) findViewById(R.id.heart);
          mSensorManager = ((SensorManager) getSystemService(SENSOR_SERVICE));
          mHeartRateSensor = mSensorManager.getDefaultSensor(Sensor.TYPE_HEART_RATE);
          mSensorManager.registerListener(this, mHeartRateSensor, SensorManager.SENSOR_DELAY_NORMAL);
          Log.i(TAG, "LISTENER REGISTERED.");
          mTextViewHeart.setText("Something here");
  
  
          mSensorManager.registerListener(sensorEventListener, mHeartRateSensor, mSensorManager.SENSOR_DELAY_FASTEST);
      }
  
  
      public void onResume(){
          super.onResume();
      }
  
      public void onAccuracyChanged(Sensor sensor, int accuracy) {
          Log.d(TAG, "onAccuracyChanged - accuracy: " + accuracy);
      }
  
      public void onSensorChanged(SensorEvent event) {
          if (event.sensor.getType() == Sensor.TYPE_HEART_RATE) {
              String msg = "" + (int)event.values[0];
              mTextViewHeart.setText(msg);
              Log.d(TAG, msg);
          }
          else
              Log.d(TAG, "Unknown sensor type");
      }
  
  }
  </pre>
  
  <p>This code is simply not working, giving me an error saying:</p>
  
  <pre>
  E/SensorManager﹕ sensor or listener is null
  </pre>
  
  <p>It works fine if I use anything else but the heart rate sensor.</p>
  
  <p>I am using:</p>
  
  <ul>
  <li>LG G4 with android API level 23</li>
  <li>LG Urbane watch (Which I know has a heart rate sensor) with Wear API level 23</li>
  </ul>
  
  <p>Thank you for your help.</p>