android: move a view on touch move

OnTouchListener.java

View.OnTouchListener touchListener = new View.OnTouchListener() {
    private int lastX = 0;
    private int lastY = 0;
    @Override
    public boolean onTouch(View v, MotionEvent event) {
        switch (event.getAction()) {
            case MotionEvent.ACTION_DOWN: {
                lastX = (int) event.getRawX();
                lastY = (int) event.getRawY();
                break;
            }
            case MotionEvent.ACTION_MOVE: {
                int dx = (int) event.getRawX() -lastX;
                int dy = (int) event.getRawY() -lastY;
                int left = v.getLeft() + dx;
                int top = v.getTop() + dy;
                int right = v.getRight() + dx;
                int bottom = v.getBottom() + dy;
                if (left < 0) {
                    left = 0;
                    right = left + v.getWidth();
                }
                if (right > screenWidth) {
                    right = screenWidth;
                    left = right - v.getWidth();
                }
                if (top < 0) {
                    top = 0;
                    bottom = top + v.getHeight();
                }
                if (bottom > screenHeight) {
                    bottom = screenHeight;
                    top = bottom - v.getHeight();
                }
                v.layout(left, top, right, bottom);
                lastX = (int) event.getRawX();
                lastY = (int) event.getRawY();
                break;
            }
            case MotionEvent.ACTION_UP: {
                break;
            }
        }
        return true;
    }
};