com.unity.uiextensions/Scripts/ReorderableList/ReorderableList.cs

/// Credit Ziboo
/// Sourced from - http://forum.unity3d.com/threads/free-reorderable-list.364600/

using System;
using UnityEngine.Events;

namespace UnityEngine.UI.Extensions
{
    [AddComponentMenu("UI/Extensions/Re-orderable list")]
    public class ReorderableList : MonoBehaviour
    {
        public LayoutGroup ContentLayout;

        public bool IsDraggable = true;
        public RectTransform DraggableArea;
        public bool CloneDraggedObject = false;

        public bool IsDropable = true;


        public ReorderableListHandler OnElementDropped = new ReorderableListHandler();

        private RectTransform _content;
        private ReorderableListContent _listContent;

        public RectTransform Content
        {
            get
            {
                if (_content == null)
                {
                    _content = ContentLayout.GetComponent<RectTransform>();
                }
                return _content;
            }
        }

        private void Awake()
        {
            if (ContentLayout == null)
            {
                Debug.LogError("You need to have a LayoutGroup content set for the list", gameObject);
                return;
            }
            if (DraggableArea == null)
            {
                Debug.LogError("You need to set a draggable area for the list", gameObject);
                return;
            }
            _listContent = ContentLayout.gameObject.AddComponent<ReorderableListContent>();
            _listContent.Init(this);
        }

        #region Nested type: ReorderableListEventStruct

        [Serializable]
        public struct ReorderableListEventStruct
        {
            public GameObject DropedObject;
            public int FromIndex;
            public ReorderableList FromList;
            public bool IsAClone;
            public GameObject SourceObject;
            public int ToIndex;
            public ReorderableList ToList;
        }

        #endregion

        #region Nested type: ReorderableListHandler

        [Serializable]
        public class ReorderableListHandler : UnityEvent<ReorderableListEventStruct>
        {
        }

        #endregion
    }
}