Handling Shake Events

Here is my implementation of shake detection for android.

    package com.android.sensor;
     
    import java.util.List;
     
    import android.hardware.Sensor;
    import android.hardware.SensorEvent;
    import android.hardware.SensorEventListener;
    import android.hardware.SensorManager;
    import android.util.Log;
     
    public class AccelerometerListener implements SensorEventListener {
     
    private SensorManager sensorManager;
    private List sensors;
    private Sensor sensor;
    private long lastUpdate = -1;
    private long currentTime = -1;
     
    private float last_x, last_y, last_z;
    private float current_x, current_y, current_z, currenForce;
    private static final int FORCE_THRESHOLD = 900;
    private final int DATA_X = SensorManager.DATA_X;
    private final int DATA_Y = SensorManager.DATA_Y;
    private final int DATA_Z = SensorManager.DATA_Z;
     
    public AccelerometerListener(Activity parent) {
    SensorManager sensorService = (SensorManager) parent.getSystemService(Context.SENSOR_SERVICE);
    this.sensorManager = sensorManager;
    this.subscriber = subscriber;
    this.sensors = sensorManager.getSensorList(Sensor.TYPE_ACCELEROMETER);
    if (sensors.size() > 0) {
    sensor = sensors.get(0);
    }
    }
    public void start () {
    if (sensor!=null) {
    sensorManager.registerListener(this, sensor, SensorManager.SENSOR_DELAY_GAME);
    }
    }
     
    public void stop () {
    sensorManager.unregisterListener(this);
    }
     
    public void onAccuracyChanged(Sensor s, int valu) {
     
     
    }
    public void onSensorChanged(SensorEvent event) {
     
    if (event.sensor.getType() != Sensor.TYPE_ACCELEROMETER || event.values.length < 3)
    return;
     
    currentTime = System.currentTimeMillis();
     
    if ((currentTime - lastUpdate) > 100) {
    long diffTime = (currentTime - lastUpdate);
    lastUpdate = currentTime;
     
    current_x = event.values[DATA_X];
    current_y = event.values[DATA_Y];
    current_z = event.values[DATA_Z];
     
    currenForce = Math.abs(current_x+current_y+current_z - last_x - last_y - last_z) / diffTime * 10000;
     
    if (currenForce > FORCE_THRESHOLD) {
     
    // Device has been shaken now go on and do something
    // you could now inform the parent activity ...
     
    }
    last_x = current_x;
    last_y = current_y;
    last_z = current_z;
     
    }
    }
     
    }