Help adding (UI) events at RunTime

Hello everybody, I've been following some inventory tutorial and making some changes here and there, but now I have run into a bit of a problem.

I have an inventory that dynamically creates gameObjects for its slots and adds various Pointer Events to them (OnDragBegin, etc.). However the trouble I have here is that left and rightclick do exactly the same thing, while I might want only left click to start dragging the item or maybe right click to just drag a single item and not the whole stack.

I think I need the Pointer Event Data to differentiate between left and right click dragging.

Some of the code I am currently using:

Code (CSharp):

1.     protected void AddEvent(GameObject obj, EventTriggerType type, UnityAction<BaseEventData> action)
2.     {
3.         EventTrigger trigger = obj.GetComponent<EventTrigger>();
4.         if (!trigger) { Debug.LogWarning("No EventTrigger component found!"); return; }
5.         var eventTrigger = new EventTrigger.Entry { eventID = type };
6.         eventTrigger.callback.AddListener(action);
7.         trigger.triggers.Add(eventTrigger);
8.     }

Code (CSharp):

1. private void CreateSlot(int i, InventorySlot slot)
2.     {
3.         var obj = Instantiate(inventoryPrefab, layoutGroup.transform);
4.  
5.         AddEvent(obj, EventTriggerType.PointerEnter, delegate { OnEnter(obj); });
6.         AddEvent(obj, EventTriggerType.PointerExit, delegate { OnExit(obj); });
7.         AddEvent(obj, EventTriggerType.BeginDrag, delegate { OnBeginDrag(obj);});
8.         AddEvent(obj, EventTriggerType.EndDrag, delegate { OnEndDrag(obj); });
9.         AddEvent(obj, EventTriggerType.Drag, delegate { OnDrag(obj); });
10.  
11.         GameObjectToInventorySlot.Add(obj, slot);
12.         InventorySlotToGameObject.Add(slot, obj);
13.     }

Code (CSharp):

1.     public void OnBeginDrag(GameObject obj)
2.     {
3.         if (GameObjectToInventorySlot[obj].item.Id >= 0)
4.         {
5.             var mouseObject = Instantiate(mouseItemPrefab, Vector2.zero, Quaternion.identity, GetComponentInParent<Canvas>().transform);
6.             var img = mouseObject.GetComponent<Image>();
7.             img.sprite = GetItemSprite(GameObjectToInventorySlot[obj]);
8.             img.raycastTarget = false;
9.             MouseData.tempItemBeingDragged = mouseObject;
10.         }
11.     }

I really don't know how to dynamically add the event that also passes me the Pointer Event data. I can create a script using the needed interfaces (IBeginDraghandler, etc.) but even then I would not know how to write an "Addevent" function to add them dynamically.

Help is appreciated. Thank you very much!

 

change delegate { OnEnter(obj); } to e => OnEnter(e, obj)


e is the event data

edit, btw, that will allocate becasue of closure

 

Thanks this works!!! Amazing. It felt kind of unintuitive to me. Probably need to read up on Closure Allocation? Is there any resource you would recommend. I'll try to google in the mean time.

 

When a delegate needs be scoped (in this case becasue of the reference to the gameobject) it will box the delegate in a reference. That will allocate. If you can remove the gameobject and only use the data from the argument sent into the action you will remove the allocation.

 

Btw it will only allocate once, when you subscribe. So if you dont subscribe that often its probably fine.