UGUI轮播图组件实现方法详解

/// 主要关注属性、事件及函数：///  public int CurrentIndex;///  public Action<int> OnIndexChange;///  public virtual void MoveToIndex(int ind);///  public virtual void AddChild(RectTransform t);/// by yangxunusing UnityEngine;using System.Collections;using System.Collections.Generic;using UnityEngine.UI;using UnityEngine.EventSystems;using System;/// <summary>/// 轮播图组件/// </summary>[RequireComponent(typeof(RectTransform)), ExecuteInEditMode]public class Carousel : UIBehaviour, IEventSystemHandler, IBeginDragHandler, IInitializePotentialDragHandler, IDragHandler, IEndDragHandler, ICanvasElement {  /// <summary> /// 子物体size /// </summary> public Vector2 CellSize; /// <summary> /// 子物体间隔 /// </summary> public Vector2 Spacing; /// <summary> /// 方向 /// </summary> public Axis MoveAxis; /// <summary> /// Tween时的步数 /// </summary> public int TweenStepCount = 10; /// <summary> /// 自动轮播 /// </summary> public bool AutoLoop = false; /// <summary> /// 轮播间隔 /// </summary> public float LoopSpace = 1; /// <summary> /// 轮播方向--1为向左移动，-1为向右移动 /// </summary> public int LoopDir = 1; /// <summary> /// 可否拖动 /// </summary> public bool Drag = true; /// <summary> /// 位于正中的子元素变化的事件,参数为index /// </summary> public Action<int> OnIndexChange; /// <summary> /// 当前处于正中的元素 /// </summary> public int CurrentIndex {  get {   return m_index;  } }  private bool m_Dragging = false; private bool m_IsNormalizing = false; private Vector2 m_CurrentPos; private int m_currentStep = 0; private RectTransform viewRectTran; private Vector2 m_PrePos; private int m_index = 0,m_preIndex = 0; private RectTransform header; private bool contentCheckCache = true;  private float currTimeDelta = 0; private float viewRectXMin {  get{   Vector3[] v = new Vector3[4];   viewRectTran.GetWorldCorners(v);   return v[0].x;  } } private float viewRectXMax {  get {   Vector3[] v = new Vector3[4];   viewRectTran.GetWorldCorners(v);   return v[3].x;  } } private float viewRectYMin {  get {   Vector3[] v = new Vector3[4];   viewRectTran.GetWorldCorners(v);   return v[0].y;  } } private float viewRectYMax {  get {   Vector3[] v = new Vector3[4];   viewRectTran.GetWorldCorners(v);   return v[2].y;  } }  public int CellCount {  get {   return transform.childCount;  } } protected override void Awake() {  base.Awake();  viewRectTran = GetComponent<RectTransform>();  header = GetChild(viewRectTran, 0); } public void resizeChildren() {  //init child size and pos  Vector2 delta;  if (MoveAxis == Axis.Horizontal) {   delta = new Vector2(CellSize.x + Spacing.x, 0);  }  else {   delta = new Vector2(0, CellSize.y + Spacing.y);  }  for (int i = 0; i < CellCount; i++) {   var t = GetChild(viewRectTran, i);   if (t) {    t.localPosition = delta * i;    t.sizeDelta = CellSize;   }  }  m_IsNormalizing = false;  m_CurrentPos = Vector2.zero;  m_currentStep = 0; } /// <summary> /// 加子物体到当前列表的最后面 /// </summary> /// <param name="t"></param> public virtual void AddChild(RectTransform t) {  if (t!=null) {   t.SetParent(viewRectTran, false);   t.SetAsLastSibling();   Vector2 delta;   if (MoveAxis == Axis.Horizontal) {    delta = new Vector2(CellSize.x + Spacing.x, 0);   }   else {    delta = new Vector2(0, CellSize.y + Spacing.y);   }   if (CellCount == 0) {    t.localPosition = Vector3.zero;    header = t;   }   else {    t.localPosition = delta + (Vector2)GetChild(viewRectTran,CellCount-1).localPosition;   }  } } protected override void OnEnable() {  base.OnEnable();  resizeChildren();  return;  if (Application.isPlaying) {   if (ContentIsLongerThanRect()) {    int s;    do {     s = GetBoundaryState();     LoopCell(s);    } while (s != 0);   }  } } protected virtual void Update() {  if (ContentIsLongerThanRect()) {   //实现在必要时loop子元素   if (Application.isPlaying) {    int s = GetBoundaryState();    LoopCell(s);   }   //缓动回指定位置   if (m_IsNormalizing && EnsureListCanAdjust()) {    if (m_currentStep == TweenStepCount) {     m_IsNormalizing = false;     m_currentStep = 0;     m_CurrentPos = Vector2.zero;     return;    }    Vector2 delta = m_CurrentPos/TweenStepCount;    m_currentStep++;    TweenToCorrect(-delta);   }   //自动loop   if (AutoLoop && !m_IsNormalizing && EnsureListCanAdjust()) {    currTimeDelta += Time.deltaTime;    if (currTimeDelta>LoopSpace) {     currTimeDelta = 0;     MoveToIndex(m_index + LoopDir);    }   }   //检测index是否变化   if (MoveAxis == Axis.Horizontal) {    m_index = (int)(header.localPosition.x / (CellSize.x + Spacing.x-1));   }   else {    m_index = (int)(header.localPosition.y / (CellSize.y + Spacing.y-1));   }   if (m_index<=0) {    m_index = Mathf.Abs(m_index);   }   else {    m_index = CellCount - m_index;   }   if (m_index != m_preIndex) {    if (OnIndexChange != null) {     OnIndexChange(m_index);    }   }   m_preIndex = m_index;  } } public virtual void OnBeginDrag(PointerEventData eventData) {  if (!Drag || !contentCheckCache) {   return;  }  Vector2 vector;  if (((eventData.button == PointerEventData.InputButton.Left) && this.IsActive()) && RectTransformUtility.ScreenPointToLocalPointInRectangle(this.viewRectTran, eventData.position, eventData.pressEventCamera, out vector)) {   this.m_Dragging = true;   m_PrePos = vector;  } }  public virtual void OnInitializePotentialDrag(PointerEventData eventData) {  if (!Drag) {   return;  }  return; }  public virtual void OnDrag(PointerEventData eventData) {  if (!Drag || !contentCheckCache) {   return;  }  Vector2 vector;  if (((eventData.button == PointerEventData.InputButton.Left) && this.IsActive()) && RectTransformUtility.ScreenPointToLocalPointInRectangle(this.viewRectTran, eventData.position, eventData.pressEventCamera, out vector)) {   m_IsNormalizing = false;   m_CurrentPos = Vector2.zero;   m_currentStep = 0;   Vector2 vector2 = vector - this.m_PrePos;   Vector2 vec = CalculateOffset(vector2);   this.SetContentPosition(vec);   m_PrePos = vector;  } } /// <summary> /// 移动到指定索引 /// </summary> /// <param name="ind"></param> public virtual void MoveToIndex(int ind) {  if (m_IsNormalizing) {   return;  }  //Debug.LogFormat("{0}->{1}",m_index,ind);  if (ind == m_index) {   return;  }  this.m_IsNormalizing = true;  Vector2 offset;  if (MoveAxis == Axis.Horizontal) {   offset = new Vector2(CellSize.x + Spacing.x, 0);  }  else {   offset = new Vector2(0, CellSize.y + Spacing.y);  }  var delta = CalcCorrectDeltaPos();  int vindex = m_index;  m_CurrentPos = delta + offset * (ind - vindex);  //m_CurrentPos = -(Vector2)header.localPosition + offset * (ind - m_index);  m_currentStep = 0; } private Vector2 CalculateOffset(Vector2 delta) {  if (MoveAxis == Axis.Horizontal) {   delta.y = 0;  }  else {   delta.x = 0;  }  return delta; } private void SetContentPosition(Vector2 position) {  foreach (RectTransform i in viewRectTran) {   i.localPosition += (Vector3)position;  }  return; }  public virtual void OnEndDrag(PointerEventData eventData) {  if (!Drag || !contentCheckCache) {   return;  }  this.m_Dragging = false;  this.m_IsNormalizing = true;  m_CurrentPos = CalcCorrectDeltaPos();  m_currentStep = 0; }  public virtual void Rebuild(CanvasUpdate executing) {  return; } /// <summary> /// List是否处于可自由调整状态 /// </summary> /// <returns></returns> public virtual bool EnsureListCanAdjust() {  return !m_Dragging && ContentIsLongerThanRect(); } /// <summary> /// 内容是否比显示范围大 /// </summary> /// <returns></returns> public virtual bool ContentIsLongerThanRect() {  float contentLen;  float rectLen;  if (MoveAxis == Axis.Horizontal) {   contentLen = CellCount*(CellSize.x + Spacing.x) - Spacing.x;   rectLen = viewRectTran.rect.xMax - viewRectTran.rect.xMin;  }  else {   contentLen = CellCount * (CellSize.y + Spacing.y) - Spacing.y;   rectLen = viewRectTran.rect.yMax - viewRectTran.rect.yMin;  }  contentCheckCache = contentLen > rectLen;  return contentCheckCache; } /// <summary> /// 检测边界情况，分为0未触界，-1左(下)触界，1右(上)触界 /// </summary> /// <returns></returns> public virtual int GetBoundaryState() {  RectTransform left;  RectTransform right;  left = GetChild(viewRectTran, 0);  right = GetChild(viewRectTran, CellCount - 1);  Vector3[] l = new Vector3[4];  left.GetWorldCorners(l);  Vector3[] r = new Vector3[4];  right.GetWorldCorners(r);  if (MoveAxis == Axis.Horizontal) {   if (l[0].x>=viewRectXMin) {    return -1;   }   else if (r[3].x < viewRectXMax) {    return 1;   }  }  else {   if (l[0].y >= viewRectYMin) {    return -1;   }   else if (r[1].y < viewRectYMax) {    return 1;   }  }  return 0; } /// <summary> /// Loop列表，分为-1把最右(上)边一个移到最左(下)边，1把最左(下)边一个移到最右(上)边 /// </summary> /// <param name="dir"></param> protected virtual void LoopCell(int dir) {  if (dir == 0) {   return;  }  RectTransform MoveCell;  RectTransform Tarborder;  Vector2 TarPos;  if (dir == 1) {   MoveCell = GetChild(viewRectTran, 0);   Tarborder = GetChild(viewRectTran, CellCount - 1);   MoveCell.SetSiblingIndex(CellCount-1);  }  else {   Tarborder = GetChild(viewRectTran, 0);   MoveCell = GetChild(viewRectTran, CellCount - 1);   MoveCell.SetSiblingIndex(0);  }  if (MoveAxis == Axis.Horizontal) {   TarPos = Tarborder.localPosition + new Vector3((CellSize.x + Spacing.x) * dir, 0,0);  }  else {   TarPos = (Vector2)Tarborder.localPosition + new Vector2(0, (CellSize.y + Spacing.y) * dir);  }  MoveCell.localPosition = TarPos; } /// <summary> /// 计算一个最近的正确位置 /// </summary> /// <returns></returns> public virtual Vector2 CalcCorrectDeltaPos() {  Vector2 delta = Vector2.zero;  float distance = float.MaxValue;  foreach (RectTransform i in viewRectTran) {   var td = Mathf.Abs(i.localPosition.x) + Mathf.Abs(i.localPosition.y);   if (td<=distance) {    distance = td;    delta = i.localPosition;   }   else {    break;   }  }  return delta; } /// <summary> /// 移动指定增量 /// </summary> protected virtual void TweenToCorrect(Vector2 delta) {  foreach (RectTransform i in viewRectTran) {   i.localPosition += (Vector3)delta;  } } public enum Axis {  Horizontal,  Vertical } private static RectTransform GetChild(RectTransform parent, int index) {  if (parent == null||index>=parent.childCount) {   return null;  }  return parent.GetChild(index) as RectTransform; }}