Unity 工具类ScrollView拖拽滑动翻页

简介：

在进行UI设计的时候，经常会使用Unity中UI提供的ScrollView，类似Android中的ScrollView，在进行图片预览，多个翻页的时候，能实现很好的效果。

该类中根据Unity的EventSystems中拖拽事件，实现对页码的滑动监听，在使用的时候，新建UI--->ScrollView，把该类组件添加到ScrollView上，把对应的content加入该脚本中的content，调整ScrollView和Content，设置单个滑动页的宽度，拖拽的阈值，即可监听到拖拽，如果是动态实例化ScrollView中的child，需设置当前最大页码数。SetCurIndex可以实现直接定位到当前页码对应的滑动页，代码比较简单，直接贴出来。

public class ScrollViewListener : MonoBehaviour, IDragHandler, IBeginDragHandler, IEndDragHandler
    {
		//滑动方向
        public enum MoveDirection
        {
            None = 0,
            Left,
            Right,
        }
        public float SingleItemWidth;//单个滑动页的宽度
        public RectTransform content;//当前ScrollView的Content
        public float DragMinValue = 5f;//拖动过程中允许的最小的拖拽值，低于此值就不算拖拽，不执行翻页事件
        private MoveDirection direction = MoveDirection.None;
        private int CurIndex = 0;//当前页码
        private int MaxIndex = 0;//最大页码
        public bool canMove = true;//是否能移动
        private Vector3 originalPos;
        private float maxDeltaX = 0f;//取整个拖动过程中的最大值
        public Action<int> OnPageChange;//对外提供页码修改的回调
		
        /// <summary>
        /// 滑到下一页
        /// </summary>
        private void MoveToNext()
        {            
            if (direction == MoveDirection.Left)
            {
                if (CurIndex < MaxIndex)
                {                    
                    CurIndex++;
                    canMove = false;
                    content.DOLocalMoveX(content.localPosition.x - SingleItemWidth, 1f).OnComplete(() =>
                    {
                        if (null != OnPageChange)
                        {
                            OnPageChange(CurIndex);
                        }
                        canMove = true;
                    });
                }
            }
            else if (direction == MoveDirection.Right)
            {
                if (CurIndex > 0)
                {
                    CurIndex--;
                    canMove = false;
                    content.DOLocalMoveX(content.localPosition.x + SingleItemWidth, 1f).OnComplete(() =>
                    {
                        if (null != OnPageChange)
                        {
                            OnPageChange(CurIndex);
                        }
                        canMove = true;
                    });
                }
            }
        }
		
        /// <summary>
        /// 设置当前滑动列表的页数的最大值
        /// </summary>
        /// <param name="max"></param>
        public void SetMaxIndex(int max)
        {
            MaxIndex = max - 1;//最大下标值为页数减1
        }

        /// <summary>
        /// 设置当前页
        /// </summary>
        /// <param name="index"></param>
        public void SetCurIndex(int index)
        {
            CurIndex = index;
            float x = content.localPosition.x - SingleItemWidth * CurIndex;
            content.localPosition = new Vector3(x, content.localPosition.y, content.localPosition.z);
        }

        public void ResetPosition()
        {
            content.localPosition = originalPos;
        }
		
        private void Awake()
		{
            CurIndex = 0;
            originalPos = content.localPosition;
        }

        public void OnDrag(PointerEventData eventData)
        {
            if (Mathf.Abs(eventData.delta.x) > maxDeltaX)
            {
                maxDeltaX = Mathf.Abs(eventData.delta.x);
            }
        }

        public void OnBeginDrag(PointerEventData eventData)
        {
            if (eventData.delta.x > 0)
            {
                direction = MoveDirection.Right;
            }
            else if (eventData.delta.x < 0)
            {
                direction = MoveDirection.Left;
            }
            else
            {
                direction = MoveDirection.None;
            }
            if (Mathf.Abs(eventData.delta.x) > maxDeltaX)
            {
                maxDeltaX = Mathf.Abs(eventData.delta.x);
            }
        }

        public void OnEndDrag(PointerEventData eventData)
        {
            if (Mathf.Abs(eventData.delta.x) > maxDeltaX)
            {
                maxDeltaX = Mathf.Abs(eventData.delta.x);
            }
            if (maxDeltaX > DragMinValue)
            {
                //计算下一页的目的点 然后移动
                if (canMove)
                {
                    MoveToNext();
                }                
            }
            maxDeltaX = 0f;
        }
    }