Unity之ScrollRect滑动居中

先上效果图

这里同时支持水平方向和垂直方向，同时ScrollRect支持使用GridLayoutGroup、HorizontalLayoutGroup、VerticalLayoutGroup三种LayoutGroup，不过水平方向的ScrollRect不支持VerticalLayoutGroup，垂直方向的ScrollRect不支持HorizontalLayoutGroup，当然也不存在这两种情况。

由于这里是通过对ScrollRect的content的localPosition做了插值移动，因此ScrollRect的中心点设置必须跟我这保持一致。

下面直接上代码：

using System;using System.Collections;using System.Collections.Generic;using UnityEngine;using UnityEngine.EventSystems;using UnityEngine.UI;public enum ScrollDir{    Horizontal,    Vertical}public class ScrollRectCenter : MonoBehaviour , IEndDragHandler,IDragHandler,IBeginDragHandler{    public ScrollDir Dir = ScrollDir.Horizontal;    /// <summary>    /// 是否正在居中    /// </summary>    private bool _isCentering = false;    /// <summary>    /// 居中过程移动速度    /// </summary>    public float MoveToCenterSpeed = 10f;    private ScrollRect _scrollView;    private Transform _content;    private List<float> _childrenPos = new List<float>();    private float _targetPos;    /// <summary>    /// 当前中心child索引    /// </summary>    private int _curCenterChildIndex = -1;    /// <summary>    /// 当前中心ChildItem    /// </summary>    public GameObject CurCenterChildItem    {        get        {            GameObject centerChild = null;            if (_content != null && _curCenterChildIndex >= 0 && _curCenterChildIndex < _content.childCount)            {                centerChild = _content.GetChild(_curCenterChildIndex).gameObject;            }            return centerChild;        }    }    void Awake()    {        _scrollView = GetComponent<ScrollRect>();        if (_scrollView == null)        {            Debug.LogError("ScrollRect is null");            return;        }        _content = _scrollView.content;        LayoutGroup layoutGroup = null;        layoutGroup = _content.GetComponent<LayoutGroup>();        if (layoutGroup == null)        {            Debug.LogError("LayoutGroup component is null");        }        _scrollView.movementType = ScrollRect.MovementType.Unrestricted;        float spacing = 0f;        //根据dir计算坐标，Horizontal：存x，Vertical：存y        switch (Dir)        {            case ScrollDir.Horizontal:                if (layoutGroup is HorizontalLayoutGroup)                {                    float childPosX = _scrollView.GetComponent<RectTransform>().rect.width * 0.5f - GetChildItemWidth(0) * 0.5f;                    spacing = (layoutGroup as HorizontalLayoutGroup).spacing;                    _childrenPos.Add(childPosX);                    for (int i = 1; i < _content.childCount; i++)                    {                        childPosX -= GetChildItemWidth(i) * 0.5f + GetChildItemWidth(i - 1) * 0.5f + spacing;                        _childrenPos.Add(childPosX);                    }                }                else if (layoutGroup is GridLayoutGroup)                {                    GridLayoutGroup grid = layoutGroup as GridLayoutGroup;                    float childPosX = _scrollView.GetComponent<RectTransform>().rect.width * 0.5f - grid.cellSize.x * 0.5f;                    _childrenPos.Add(childPosX);                    for (int i = 0; i < _content.childCount - 1; i++)                    {                        childPosX -= grid.cellSize.x + grid.spacing.x;                        _childrenPos.Add(childPosX);                    }                }                else                {                    Debug.LogError("Horizontal ScrollView is using VerticalLayoutGroup");                }                break;            case ScrollDir.Vertical:                if (layoutGroup is VerticalLayoutGroup)                {                    float childPosY = -_scrollView.GetComponent<RectTransform>().rect.height * 0.5f + GetChildItemHeight(0) * 0.5f;                    spacing = (layoutGroup as VerticalLayoutGroup).spacing;                    _childrenPos.Add(childPosY);                    for (int i = 1; i < _content.childCount; i++)                    {                        childPosY += GetChildItemHeight(i) * 0.5f + GetChildItemHeight(i - 1) * 0.5f + spacing;                        _childrenPos.Add(childPosY);                    }                }                else if (layoutGroup is GridLayoutGroup)                {                    GridLayoutGroup grid = layoutGroup as GridLayoutGroup;                    float childPosY = -_scrollView.GetComponent<RectTransform>().rect.height * 0.5f + grid.cellSize.y * 0.5f;                    _childrenPos.Add(childPosY);                    for (int i = 1; i < _content.childCount; i++)                    {                        childPosY += grid.cellSize.y + grid.spacing.y;                        _childrenPos.Add(childPosY);                    }                }                else                {                    Debug.LogError("Vertical ScrollView is using HorizontalLayoutGroup");                }                break;        }    }    private float GetChildItemWidth(int index)    {        return (_content.GetChild(index) as RectTransform).sizeDelta.x;    }    private float GetChildItemHeight(int index)    {        return (_content.GetChild(index) as RectTransform).sizeDelta.y;    }    void Start ()     {    }    void Update ()     {        if (_isCentering)        {            Vector3 v = _content.localPosition;            switch (Dir)            {                case ScrollDir.Horizontal:                    v.x = Mathf.Lerp(_content.localPosition.x, _targetPos, MoveToCenterSpeed * Time.deltaTime);                    _content.localPosition = v;                    if (Math.Abs(_content.localPosition.x - _targetPos) < 0.01f)                    {                        _isCentering = false;                    }                    break;                case ScrollDir.Vertical:                    v.y = Mathf.Lerp(_content.localPosition.y, _targetPos, MoveToCenterSpeed * Time.deltaTime);                    _content.localPosition = v;                    if (Math.Abs(_content.localPosition.y - _targetPos) < 0.01f)                    {                        _isCentering = false;                    }                    break;            }        }    }    public void OnDrag(PointerEventData eventData)    {    }    public void OnEndDrag(PointerEventData eventData)    {        switch (Dir)        {            case ScrollDir.Horizontal:                _targetPos = FindClosestChildPos(_content.localPosition.x, out _curCenterChildIndex);                break;            case ScrollDir.Vertical:                _targetPos = FindClosestChildPos(_content.localPosition.y, out _curCenterChildIndex);                break;        }        _isCentering = true;    }    public void OnBeginDrag(PointerEventData eventData)    {        _isCentering = false;        _curCenterChildIndex = -1;    }    private float FindClosestChildPos(float currentPos, out int curCenterChildIndex)    {        float closest = 0;        float distance = Mathf.Infinity;        curCenterChildIndex = -1;        for (int i = 0; i < _childrenPos.Count; i++)        {            float p = _childrenPos[i];            float d = Mathf.Abs(p - currentPos);            if (d < distance)            {                distance = d;                closest = p;                curCenterChildIndex = i;            }        }        return closest;    }}

最后附上Demo下载链接：
链接：http://pan.baidu.com/s/1pLoJcjL 密码：js7g
链接如果失效，请及时评论，及时更新

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