ScrollRect.OnDrag

public void OnDrag (EventSystems.PointerEventData eventData);

Description

Handling for when the content is dragged.

using UnityEngine;
using System.Collections;
using UnityEngine.EventSystems; // Required when using event data

public class ExampleClass : MonoBehaviour, IDragHandler // required interface when using the OnDrag method.
{
    //Do this while the user is dragging this UI Element.
    public void OnDrag(PointerEventData data)
    {
        Debug.Log("Currently dragging " + this.name);
    }
}