Horizontal ScrollView paginated

I have done this in the past. You can do this with a custom listener:

public MyHorizontalScrollView(Context context, AttributeSet attrs) {
    super(context, attrs);
    setOnTouchListener(new View.OnTouchListener() {
            public boolean onTouch(View v, MotionEvent event) {
                if (event.getAction() == MotionEvent.ACTION_UP || event.getAction() == MotionEvent.ACTION_CANCEL ){
                    int scrollX = getScrollX();
                    int itemWidth = getMeasuredWidth();
                    int activeItem = ((scrollX + itemWidth / 2) / itemWidth);
                    int scrollTo = activeItem * itemWidth;
                    smoothScrollTo(scrollTo, 0);

                    return true;
                } else {
                    return false;
                }
            }
        });
    }

Pretty clear, I think. This assumes that the width of your pages is constant and equal to the width of the entire scroll.