Android: detecting fling gestures

In my app I try to capture a fling event on a view (a ScrollView to be exact, but tried with LinearLayout as well).

By setting breakpoints I can see the that the MotionEvents happen correctly up to the point where the onFling() should fire.

The event flow is as follows:

1. The view's onTouchEvent
2. The OnGestureListener's onDown
3. The OnGestureListener's onShowPress
4. The OnGestureListener's onLongPress

I'm at a loss on how to go on trying to debug something like that and Google search does not turn up much. Any pointers ?

I also attach the relevant view that should handle the gestures:

import android.content.Context;
import android.content.Intent;
import android.view.GestureDetector;
import android.view.MotionEvent;
import android.widget.ScrollView;

public class GestureScrollView extends ScrollView {
    private static int MAJOR_MOVE = 60;
    private GestureDetector gd;

    public GestureScrollView(final Context context) {
        super(context);
        gd = new GestureDetector(context,
                new GestureDetector.OnGestureListener() {

                    @Override
                    public boolean onSingleTapUp(MotionEvent e) {
                        // TODO Auto-generated method stub
                        return false;
                    }

                    @Override
                    public void onShowPress(MotionEvent e) {
                        // TODO Auto-generated method stub

                    }

                    @Override
                    public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX,
                            float distanceY) {
                        // TODO Auto-generated method stub
                        return false;
                    }

                    @Override
                    public v