how to get gravity sensor information?

i'm trying to write an app for testing sensors by my Nexus S.

well , i wrote this to show the sensors lists through a listview.

@Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        //get all sensors
        sensorManager = (SensorManager) this.getSystemService(SENSOR_SERVICE);
        sensors = sensorManager.getSensorList(Sensor.TYPE_ALL);

        setContentView(R.layout.main);

        sensorListView = (ListView) findViewById(R.id.sensor_listview);
        sensorListView.setOnItemClickListener(new OnItemClickListener() {
            public void on开发者_JS百科ItemClick(AdapterView<?> arg0, View arg1, int position,
                    long arg3) {
                showSensorInfo(sensors.get(position).getType());
            }
        });



        //set an empty adapter for ListView
        sensorNames = new ArrayAdapter<String>(getApplicationContext(),
                android.R.layout.simple_list_item_1);


        for (Sensor s : sensors) {
            sensorNames.add(s.getName());
            Log.i("sensor", s.getName());
        }
        sensorListView.setAdapter(sensorNames);
    }

i saw this ~

there is a sensor called 「Gravity Sensor」,

my question is , there are sensors CONSTANT such as :

Sensor.TYPE_ACCELEROMETER

Sensor.TYPE_GYROSCOPE

Sensor.TYPE_LIGHT .. .

and so on .But i couldn't find a CONSTANT called 「Sensor.TYPE_GRAVITY」

where is the Gravity Sensor from =..=a?? ( i'm a really newbie~ )

The gravity is measured by the accelerometer but you can look up the gravity constant (approximately 9.8m/s^2.) The method to get an accurate constant is SensorManager.STANDARD_GRAVITY You can look up the full use on http://developer.android.com/reference/android/hardware/SensorManager.html#STANDARD_GRAVITY

TYPE_GRAVITY exists: http://developer.android.com/reference/android/hardware/SensorEvent.html but its only available from Android 2.3 onwards. so check that in your app.