Move TextView only up and down

I would need to move TextView only up and down. I have this code, but using it you can move TextView in any direction:

textView.setOnTouchListener(new View.OnTouchListener() {
            public boolean onTouch(View v, MotionEvent event) {
                int eid = event.getAction();
                switch (eid) {
                    case MotionEvent.ACTION_MOVE:
                        RelativeLayout.LayoutParams layoutParams = (RelativeLayout.LayoutParams) textView.getLayoutParams();
                        int x = (int) event.getRawX();
                        int y = (int) event.getRawY();
                        layoutParams.leftMargin = x - 200;
                        layoutParams.topMargin = y - 250;
                        textView.setLayoutParams(layoutParams);
                        break;
                    default:
                        break;
                }
                return true;
            }
        });

Is there a way to move TextView only up and down?