Listener for shake events.

ShakeDetector.java

/**
 * Created by Omar on 07/03/2017.
 */

public class ShakeDetector implements SensorEventListener {
    private static final int SENSITIVITY = 18;
    private static final int INTERVAL_M = 2500;

    private SensorManager sensorManager;
    private Sensor accelerometer;
    private Listener listener;
    private float accelerometerCurrent;
    private float value;
    private long lastShake;

    public ShakeDetector(SensorManager sensorManager) {
        this.sensorManager = sensorManager;
        this.lastShake = 0;
    }

    public void setListener(Listener listener) {
        this.listener = listener;
    }

    @Override
    public void onSensorChanged(SensorEvent event) {
        float ay = event.values[1];

        float accelerometerLast = accelerometerCurrent;
        accelerometerCurrent = Math.abs(ay);
        value = value * 0.9f + accelerometerCurrent - accelerometerLast;

        if(value > SENSITIVITY){
            if(listener != null){
                long now = getTimestamp();
                if(now - lastShake > INTERVAL_M){
                    lastShake = now;
                    listener.onShake();
                }
            }
        }
    }

    @Override public void onAccuracyChanged(Sensor sensor, int accuracy) {}

    public void start() {
        if (accelerometer != null) {
            return;
        }

        accelerometer = sensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER);

        if (accelerometer != null) {
            sensorManager.registerListener(this, accelerometer, SensorManager.SENSOR_DELAY_FASTEST);
        }
    }

    public void stop() {
        if (accelerometer != null) {
            sensorManager.unregisterListener(this, accelerometer);
            accelerometer = null;
        }
    }

    private long getTimestamp(){
        return new Date().getTime();
    }

    public interface Listener {
        void onShake();
    }
}