Get double tap in background

[iacoposk8]

Hello everyone!
I would create an app for get the double tap also if the app is in background.
I create this code:

package com.example.iacopo.myapplication;

import android.app.Activity;
import android.os.Bundle;
import android.support.v4.view.GestureDetectorCompat;
import android.util.Log;
import android.view.GestureDetector;
import android.view.MotionEvent;

public class MainActivity extends Activity implements
        GestureDetector.OnGestureListener,
        GestureDetector.OnDoubleTapListener
{

    private static final String DEBUG_TAG = "Gestures";
    private GestureDetectorCompat mDetector;
    private int counter = 0;

    // Called when the activity is first created.
    @Override
    public void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        // Instantiate the gesture detector with the
        // application context and an implementation of
        // GestureDetector.OnGestureListener
        mDetector = new GestureDetectorCompat(this,this);
        // Set the gesture detector as the double tap
        // listener.
        mDetector.setOnDoubleTapListener(this);
    }

    @Override
    public boolean onTouchEvent(MotionEvent event)
    {
        this.mDetector.onTouchEvent(event);
        // Be sure to call the superclass implementation
        return super.onTouchEvent(event);
    }

    @Override
    public boolean onDoubleTap(MotionEvent event)
    {
        counter++;
        Log.d(DEBUG_TAG, String.valueOf(counter));
        //Log.d(DEBUG_TAG, "onDoubleTap: " + event.toString());
        return true;
    }

    @Override
    public boolean onDoubleTapEvent(MotionEvent event)
    {
        //Log.d(DEBUG_TAG, "onDoubleTapEvent: " + event.toString());
        return true;
    }

    @Override
    public boolean onDown(MotionEvent event)
    {
        return true;
    }

    @Override
    public boolean onFling(MotionEvent event1, MotionEvent event2, float velocityX, float velocityY)
    {
        return true;
    }

    @Override
    public void onLongPress(MotionEvent event)
    {

    }

    @Override
    public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX,
                            float distanceY)
    {
        return true;
    }

    @Override
    public void onShowPress(MotionEvent event)
    {

    }

    @Override
    public boolean onSingleTapUp(MotionEvent event)
    {
        return true;
    }

    @Override
    public boolean onSingleTapConfirmed(MotionEvent event)
    {
        return true;
    }
}

if the app is open in the log i see the number of count of double tap increase, if the app work in background the number is blocked.
There is a way for fix it? or i have to create a services? i need a grafic app and service, there is a way for create just one with both things?
Thanks