GestureDetector.SimpleOnGestureListener and GestureDetectorCompat don't work. What's wrong with my code?

Question

I'm following Detecting common gestures guide. I have linked to android-support-v4.jar library to get GestureDetectorCompat, and my code seems exactly the same as in the guide, except I'm detecting gestures in my custom view rather than in activity:

public class MyGlView extends GLSurfaceView {

    private GestureDetectorCompat m_gestureDetector = null;

    public MyGlView(Context context, AttributeSet attrs) {
        super(context, attrs);
        init(context);
    }
    public MyGlView(Context context) {
        super(context);
        init(context);
    }
    private void init(Context context) {
        if (m_gestureDetector == null)
            m_gestureDetector = new GestureDetectorCompat(context, new MyGestureListener());

        setEGLContextClientVersion(2);
        setRenderer(new DrawSurfRenderer());
        setRenderMode(RENDERMODE_CONTINUOUSLY); 
    }

@Override
    public boolean onTouchEvent(MotionEvent event) {

        m_gestureDetector.onTouchEvent(event);      
        return super.onTouchEvent(event);
    }

public class MyGestureListener extends GestureDetector.SimpleOnGestureListener {

        @Override
        public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY)
        {
            Log.e("", "OnScroll: deltaX=" + String.valueOf(e2.getX() - e1.getX()) + ", deltaY=" + String.valueOf(e2.getY() - e1.getY()));
            return true;
        }

        @Override
        public boolean onSingleTapUp(MotionEvent e)
        {
            Log.e("", "onSingleTapUp: X=" + String.valueOf(e.getX()) + ", Y=" + String.valueOf(e.getY()));
            return true;
        }

        @Override
        public void onLongPress(MotionEvent e)
        {
            Log.e("", "onLongPress: X=" + String.valueOf(e.getX()) + ", Y=" + String.valueOf(e.getY()));
        }
    }

No matter what I do with the touchscreen, I'm only getting onLongPress. In fact, when I do fast tap (quickly touching and releasing the screen) I still get onLongPress slightly after I remove my finger from the screen ( suspect that's a long tap detection delay).

What's the catch?

Answer 1

I quote Android Guide on Detecting Common Gestures:

Whether or not you use GestureDetector.OnGestureListener, it's best practice to implement an onDown() method that returns true. This is because all gestures begin with an onDown() message. If you return false from onDown(), as GestureDetector.SimpleOnGestureListener does by default, the system assumes that you want to ignore the rest of the gesture, and the other methods of GestureDetector.OnGestureListener never get called. This has the potential to cause unexpected problems in your app. The only time you should return false from onDown() is if you truly want to ignore an entire gesture.

The fact that you did not implement the onDown() method was causing side effects.