imageView.setOnTouchListener(new View.OnTouchListener() {
            @Override
            public boolean onTouch(View v, MotionEvent event) {
                if (event.getAction() == MotionEvent.ACTION_UP) {

                    //left button
                    if (event.getRawX() < width / 2 && event.getRawY() > height / 2) {
                        Toast.makeText(MainActivity.this, "Left", Toast.LENGTH_SHORT).show();
                        photos.get(++count);
                    }

                    //right button
                    if (event.getRawX() >= width / 2 && event.getRawY() > height / 2) {
                        Toast.makeText(MainActivity.this, "Right", Toast.LENGTH_SHORT).show();
                        photos.get(--count);
                    }
                }

                return true;
            }
        });