Creating clickable image on-the-fly

Question

I am trying to implement an inventory system which allows me to dynamically (i.e. during runtime) create a UI-Image as visual representation for an item which can be moved around with the mouse and snaps in place in the inventory grid. SO basically, all I am doing needs to be accessible from c#-scripts.

However, I found it excessively difficult to use the built-in systems to detect a mouse click on the 2D item with e.g. IPointerDownHandler. I also tried using OnMouseDown(), but it doesn't seem to register. I also also tried this stuff of which I understand about half, so I'm just gonna post it:

     //Create new trigger
     EventTrigger evtrig=gameObject.AddComponent<EventTrigger>();

     //Create a new event to add to the trigger
     EventTrigger.TriggerEvent trigev=new EventTrigger.TriggerEvent();
     trigev.AddListener((eventData) => OnPointerDown((PointerEventData)eventData)); //link to onpointerdown function

     EventTrigger.Entry entry = new EventTrigger.Entry() { callback = trigev, eventID = EventTriggerType.PointerDown };

     if (evtrig.delegates==null) evtrig.delegates=new List<EventTrigger.Entry>();
     evtrig.delegates.Add(entry);

So I guess my question is this: Has anyone had success implementing a similar system? (The main point being that it has to be created through scripting) Maybe I am just plain wrong with my sample code here, too

Answer 1

I've made an extension method for it. Simply include this class somewhere in your project:

 using UnityEngine.EventSystems;
 
 public static class ExtensionMethods
 {
     public static void AddListener (this EventTrigger trigger, EventTriggerType eventType, System.Action<PointerEventData> listener)
     {
         EventTrigger.Entry entry = new EventTrigger.Entry();
         entry.eventID = eventType;
         entry.callback.AddListener(data => listener.Invoke((PointerEventData)data));
         trigger.triggers.Add(entry);
     }
 }

Then use it like this:

 using UnityEngine;
 using UnityEngine.EventSystems;
 
 public class UIController : MonoBehaviour
 {
     void Start ()
     {
         EventTrigger myEventTrigger = GetComponent<EventTrigger> (); //you need to have an EventTrigger component attached this gameObject
         myEventTrigger.AddListener (EventTriggerType.PointerClick, onClickListener);
     }
 
     void onClickListener (PointerEventData eventData)
     {
         //put your logic here...
     }
 }

Creating clickable image on-the-fly

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