SimpleOnGestureListener doesn't detect onFling on SurfaceView (but does detect onDown)

Question

onDown works fine, it's detected and the debug text appears in Log. The onFling however is never called, both in the emulator on the latest API and my phone on API 16 (no toast or debug message).

I've followed Google's example to the letter (third example on this page) and I don't think it's a fragmentation issue as it's not working on both a relatively old and a new API.

I've checked other related questions here, my onDown is returning true so it should propagate.

My onTouchEvent:

@Override 
public boolean onTouchEvent(MotionEvent event) {
    this.mDetector.onTouchEvent(event);
    return super.onTouchEvent(event);
}

Here's my SimpleOnGestureListener:

class MyGestureListener extends GestureDetector.SimpleOnGestureListener {
    private static final String DEBUG_TAG = "GESTURE"; 

    @Override
    public boolean onDown(MotionEvent event) { 
        Log.d("DOWN", "CATCH");
        return true;
    }

    @Override
    public boolean onFling(MotionEvent event1, MotionEvent event2, float velocityX, float velocityY) {
        Toast.makeText(context, "FLING", Toast.LENGTH_SHORT).show();
        Log.d("DOWN", "CATCH");
        return true;
    }
}

Any indications would be greatly appreciated.

NOTE: This is in an extended SurfaceView if it makes any difference.