Old question, but I'm answering here for the sake of others that find this question.
First off, following @andrew-morton link is exactly what I needed, but was in pseudo code, so here is Java for Android!
Second: If you can (you're min API Lvl is 9 or higher), simply use the Sensor.TYPE_GRAVITY. As it is already smoothed out. If you need to support older API Lvls (like I had to), this code should do the trick!
Lastly: This code snippet is somewhat modified from what I am using it for, if you want to use this for yourself, you'll need to create a getter for the Vector3 gravity.
Notes: I've found that a rolling average of 5 (MAX_SAMPLE_SIZE) is quite smooth. 10 is even more smooth, but you start to notice lag.
import android.hardware.Sensor;
import android.hardware.SensorEvent;
import android.hardware.SensorEventListener;
import android.hardware.SensorManager;
import java.util.ArrayList;
import java.util.List;
/**
* Created by andy on 6/14/14.
*/
public class AndroidGravityUpdate implements SensorEventListener {
private SensorManager sensorManager;
Vector3 gravity;
List<Float>[] rollingAverage = new List[3];
private static final int MAX_SAMPLE_SIZE = 5;
AndroidGravityUpdate( SensorManager sensorManager ) {
this.gravity = new Vector3();
this.sensorManager = sensorManager;
if(sensorManager.getSensorList(Sensor.TYPE_GRAVITY).size() > 0){
sensorManager.registerListener(
this,
sensorManager.getDefaultSensor(Sensor.TYPE_GRAVITY),
SensorManager.SENSOR_DELAY_GAME
);
} else if( sensorManager.getSensorList(Sensor.TYPE_ACCELEROMETER).size() > 0) {
rollingAverage[0] = new ArrayList<Float>();
rollingAverage[1] = new ArrayList<Float>();
rollingAverage[2] = new ArrayList<Float>();
sensorManager.registerListener(
this,
sensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER),
SensorManager.SENSOR_DELAY_GAME
);
}
}
@Override
public void onSensorChanged(SensorEvent event) {
if (event.sensor.getType()==Sensor.TYPE_GRAVITY){
gravity.z = event.values[0];
gravity.x = event.values[1];
gravity.y = - event.values[2];
}
else if ( event.sensor.getType()==Sensor.TYPE_ACCELEROMETER) {
//For whatever reason, my Samsung only has "Accelerometer"
// But it is incredibly rough, so attempting to smooth
// it out with rolling averages.
rollingAverage[0] = roll(rollingAverage[0], event.values[0]);
rollingAverage[1] = roll(rollingAverage[1], event.values[1]);
rollingAverage[2] = roll(rollingAverage[2], -event.values[2]);
gravity.z = averageList(rollingAverage[0]);
gravity.x = averageList(rollingAverage[1]);
gravity.y = averageList(rollingAverage[2]);
}
}
public List<Float> roll(List<Float> list, float newMember){
if(list.size() == MAX_SAMPLE_SIZE){
list.remove(0);
}
list.add(newMember);
return list;
}
public float averageList(List<Float> tallyUp){
float total=0;
for(float item : tallyUp ){
total+=item;
}
total = total/tallyUp.size();
return total;
}
@Override
public void onAccuracyChanged(Sensor sensor, int accuracy) {
}
}
class Vector3 {
float x;
float y;
float z;
}