non funziona

package g2k.sensor.touchme;

import android.hardware.Sensor;
import android.hardware.SensorEvent;
import android.hardware.SensorEventListener;
import android.hardware.SensorManager;
import android.media.AudioManager;
import android.media.ToneGenerator;
import android.os.Bundle;
import android.app.Activity;
import android.content.Context;
import android.view.Menu;
import android.view.WindowManager.LayoutParams;

public class Unlock extends Activity implements SensorEventListener {
    private SensorManager mSensorManager;
    private Sensor ProxymitySensor ;
    private ToneGenerator tg = new ToneGenerator(AudioManager.STREAM_NOTIFICATION, 100);


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_unlock);

        mSensorManager = (SensorManager) getSystemService(Context.SENSOR_SERVICE);
        ProxymitySensor = mSensorManager.getDefaultSensor(Sensor.TYPE_PROXIMITY);
        mSensorManager.registerListener(this, ProxymitySensor,SensorManager.SENSOR_DELAY_NORMAL);


    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.unlock, menu);
        return true;
    }


      @Override
      public final void onSensorChanged(SensorEvent event) {
        Object sensordata = event.values[0];
        // Do something with this sensor data.
        if (event.values[0] == event.sensor.getMaximumRange()){
                        PlaySound();
                        UnlockMe();
        }
      }

      private void PlaySound() {
             tg.startTone(ToneGenerator.TONE_PROP_BEEP);
      }

      private void UnlockMe(){
          // try to unlock the phone
           getWindow().addFlags(LayoutParams.FLAG_DISMISS_KEYGUARD);
           getWindow().addFlags(LayoutParams.FLAG_SHOW_WHEN_LOCKED);
           getWindow().addFlags(LayoutParams.FLAG_TURN_SCREEN_ON);
           // nothing happen :(
      }



      @Override
      public void onAccuracyChanged(Sensor arg0, int arg1) {
        // TODO Auto-generated method stub
      }


}