问onSensorChanged()中的值不会存储在变量中

EN

  // Storage for Sensor readings
  public float[] mGravity = new float[3];
  public float[] mGeomagnetic = new float[3];

  public void registerSensors(Context context) {
        // First, get an instance of the SensorManager
        SensorManager sMan = (SensorManager) context.getSystemService(Context.SENSOR_SERVICE);

        // Second, get the sensor you're interested in
        Sensor magnetField = sMan.getDefaultSensor(Sensor.TYPE_MAGNETIC_FIELD);

        // Get a reference to the accelerometer
        Sensor accelerometer = sMan.getDefaultSensor(Sensor.TYPE_ACCELEROMETER);

        // Third, implement a SensorEventListener class
        SensorEventListener magnetListener = new SensorEventListener() {
            public void onAccuracyChanged(Sensor sensor, int accuracy) {
                // do things if you're interested in accuracy changes
            }

            public void onSensorChanged(SensorEvent event) {
                mGravity = new float[3];
                //Log.i("LocationUpdater", "magnetometer updated");
                System.arraycopy(event.values, 0, mGravity, 0, 3);
                //Log.i("LocationUpdater", Float.toString(mGravity[0]));

            }
        };

        SensorEventListener accelListener = new SensorEventListener() {
            public void onAccuracyChanged(Sensor sensor, int accuracy) {
                // do things if you're interested in accuracy changes
            }

            public void onSensorChanged(SensorEvent event) {
                mGeomagnetic = new float[3];
                //Log.i("LocationUpdater", "accelerometer updated");
                System.arraycopy(event.values, 0, mGeomagnetic, 0, 3);
            }
        };


        //mGravity[0] = 5;

        // Finally, register your listener
        sMan.registerListener(magnetListener, magnetField, SensorManager.SENSOR_DELAY_NORMAL);
        sMan.registerListener(accelListener, accelerometer, SensorManager.SENSOR_DELAY_NORMAL);

        Log.i("LocationUpdater","Listeners registered");

    }

  public double getUserDirection() {
        Log.i("LocationUpdater", Float.toString(mGravity[0]));
        if (mGravity != null && mGeomagnetic != null) {

            float rotationMatrix[] = new float[9];

        ...
  }

 SensorUpdater updater = new SensorUpdater();
 updater.startBlukii(context);
 updater.registerSensors(context);
 double direction = updater.getUserDirection();
 Log.i(LOG_TAG, Double.toString(direction));