void TouchDrag_OnPointerUpEvent(PointerEventData p, A_TouchDrag td)
    {
        if (this.state == ConstructionState.PLACING)
        {
            // Disable touch drag on pointer up.
            TouchDrag_Button tdb = (TouchDrag_Button)td;
            tdb.eventTrigger.enabled = false;

            // Drop the building.
            this.DropBuilding(this.selectedBuilding);
        }
    }
    void TouchDrag_OnPointerDownEvent(PointerEventData p, A_TouchDrag td)
    {
        if (this.state == ConstructionState.SELECTING)
        {
            // Disable all further construction, except for current button.
            foreach (A_TouchDrag button in this.constructionButtons)
            {
                if (button != td)
                {
                    button.eventTrigger.enabled = false;
                }
            }

            // Create the building passed by the touch drag button.
            TouchDrag_Button tdb = (TouchDrag_Button)td;
            if (tdb != null)
            {
                this.CreateBuilding(tdb.prefabToCreate);
            }
        }
    }