Android drawable swiping not working (from beginners sample code)

package vf.base;


import android.app.Activity;
import android.content.res.TypedArray;
import android.os.Bundle;
import android.view.MotionEvent;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.ViewFlipper;


public class MainActivity extends Activity {


    private ViewFlipper viewFlipper;
    private TypedArray pics;
    private OnSwipeTouchListener onSwipeTouchListener;


    /**
     * Called when the activity is first created.
     */
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        pics = getResources().obtainTypedArray(R.array.pics);
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);


        viewFlipper = (ViewFlipper) findViewById(R.id.viewFlipper);
        for (int i = 0; i < pics.length(); i++) {
            AddViewFlipper(i);
        }


        onSwipeTouchListener = new OnSwipeTouchListener(this) {
            @Override
            public void onSwipeRight() {
                viewFlipper.showNext();
            }
}


            @Override
            public void onSwipeLeft() {
                viewFlipper.showPrevious();
            }
        };


        viewFlipper.setOnTouchListener(onSwipeTouchListener);
    }


    private void AddViewFlipper(int position) {
        ImageView imageView = new ImageView(MainActivity.this);
        imageView.setImageResource(position);
        ViewGroup.LayoutParams imageParams = new ViewGroup.LayoutParams(
                ViewGroup.LayoutParams.MATCH_PARENT,            ViewGroup.LayoutParams.MATCH_PARENT);
        imageView.setLayoutParams(imageParams);


        viewFlipper.addView(imageView);
    }


    @Override
    public boolean dispatchTouchEvent(MotionEvent ev) {
        onSwipeTouchListener.gestureDetector.onTouchEvent(ev);
        return super.dispatchTouchEvent(ev);
    }
}

package vf.base;


import android.content.Context;
import android.view.GestureDetector;
import android.view.MotionEvent;
import android.view.View;


public class OnSwipeTouchListener implements View.OnTouchListener {
    public GestureDetector gestureDetector;


    public OnSwipeTouchListener(Context context) {
        gestureDetector = new GestureDetector(context, new GestureListener());
    }


    public void onSwipeLeft() {
    }


    public void onSwipeRight() {
    }


    public boolean onTouch(View v, MotionEvent event) {
        return gestureDetector.onTouchEvent(event);
    }


    private final class GestureListener extends GestureDetector.SimpleOnGestureListener {


        private static final int SWIPE_DISTANCE_THRESHOLD = 100;
        private static final int SWIPE_VELOCITY_THRESHOLD = 100;


        @Override
        public boolean onDown(MotionEvent e) {
            return true;
        }
@Override
        public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {
            float distanceX = e2.getX() - e1.getX();
            float distanceY = e2.getY() - e1.getY();
            if (Math.abs(distanceX) > Math.abs(distanceY) && Math.abs(distanceX) > SWIPE_DISTANCE_THRESHOLD
                    && Math.abs(velocityX) > SWIPE_VELOCITY_THRESHOLD) {
                if (distanceX > 0)
                    onSwipeRight();
                else
                    onSwipeLeft();
                return true;
            }
            return false;
        }


    }
}

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical">


    <ViewFlipper
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        android:id="@+id/viewFlipper"
        android:layout_alignParentTop="true"
        android:layout_alignParentStart="true" />


</LinearLayout>