Unity - Detect click on canvas using graphic raycaster -- via: http://answers.unity.com/answers/1526703/view.html

CheckClicks.cs

 using System.Collections.Generic;
 
 using UnityEngine;
 using UnityEngine.UI;
 using UnityEngine.EventSystems;
 
 public class CheckClicks : MonoBehaviour
 {
     // Normal raycasts do not work on UI elements, they require a special kind
     GraphicRaycaster raycaster;
 
     void Awake()
     {
         // Get both of the components we need to do this
         this.raycaster = GetComponent<GraphicRaycaster>();
     }
 
     void Update()
     {
         //Check if the left Mouse button is clicked
         if (Input.GetKeyDown(KeyCode.Mouse0))
         {
             //Set up the new Pointer Event
             PointerEventData pointerData = new PointerEventData(EventSystem.current);
             List<RaycastResult> results = new List<RaycastResult>();
 
             //Raycast using the Graphics Raycaster and mouse click position
             pointerData.position = Input.mousePosition;
             this.raycaster.Raycast(pointerData, results);
 
             //For every result returned, output the name of the GameObject on the Canvas hit by the Ray
             foreach (RaycastResult result in results)
             {
                 Debug.Log("Hit " + result.gameObject.name);
             }
         }
     }
 }