// Detect swipes
if(e.getAction() == MotionEvent.ACTION_DOWN) {
    startTime = timing.getCurTimeMillis() / 1000;
    startX = touchX;
    startY = touchY;
}

float dx = startX - touchX;
float dy = startY - touchY;

if(dx < -15) { // left-swipe
    if(dy > -45 && dy < 45)
        parentGameHost.onSwipe(SIDE.LEFT);
}

if(dx > 15) { // right-swipe
    if(dy > -45 && dy < 45)
        parentGameHost.onSwipe(SIDE.RIGHT);
}

if(dy > -15) { // up-swipe
     if(dx > -45 && dx < 45)
         parentGameHost.onSwipe(SIDE.UP);
}

if(dy < 15) { // down-swipe
    if(dx > -45 && dx < 45)
        parentGameHost.onSwipe(SIDE.DOWN);
}