//--------------------------------------------------
// 公有方法
//--------------------------------------------------
// 直接设置指定索引的页面到视口
public void SetTo(int index)
{
// Disabled 状态下留待 enable 后执行
if (!isActiveAndEnabled)
{
newIndex = index;
return;
}
SetTargetIndex(index);
if (isDragging)
{
return;
}
// 当前位置 layout 和 viewport 左上角之间的距离（有方向）
Vector2 cornerDist = UILayoutUtility.GetLayoutLT2ViewportLT(layoutRectTransform, viewport);
if (direction == Direction.Horizontal && !Mathf.Approximately(cornerDist.x, targetCornerDistance))
{
SetLayoutAnchoredPosition(layoutRectTransform.anchoredPosition
+ new Vector2(cornerDist.x - targetCornerDistance, 0));
}
else if (direction == Direction.Vertical && !Mathf.Approximately(cornerDist.y, targetCornerDistance))
{
SetLayoutAnchoredPosition(layoutRectTransform.anchoredPosition
+ new Vector2(0, cornerDist.y - targetCornerDistance));
}
}
/// <summary>
/// 获取页面中心到 viewport 中心在滚动方向上的距离（带符号）。
/// </summary>
private float GetPageCenterToViewportCenter(int pageIndex)
{
Vector2 delta = UILayoutUtility.GetItemCenterToViewportCenter(layoutRectTransform, viewport,
scrolltoableLayout, pageIndex);
return(direction == Direction.Horizontal ? delta.x : delta.y);
}
/// <summary>
/// 将页面惯性滚动到目标位置。
/// </summary>
private void ScrollToTargetPosition(float deltaTime)
{
// 当前位置 layout 和 viewport 左上角之间的距离（有方向）
Vector2 cornerDist = UILayoutUtility.GetLayoutLT2ViewportLT(layoutRectTransform, viewport);
// 进行横向滚动
if (direction == Direction.Horizontal && !Mathf.Approximately(cornerDist.x, targetCornerDistance))
{
float speed = Mathf.Max(minScrollSpeed, Mathf.Abs(smoothVelocity.x)); // 滚动速度不低于下限
float delta = cornerDist.x - targetCornerDistance;
float step = Mathf.Abs(speed) * deltaTime * Mathf.Sign(delta);
if ((delta < 0 && step < delta) || (delta > 0 && step > delta))
{
step = delta;
}
SetLayoutAnchoredPosition(layoutRectTransform.anchoredPosition + new Vector2(step, 0));
}
// 进行纵向滚动
else if (direction == Direction.Vertical && !Mathf.Approximately(cornerDist.y, targetCornerDistance))
{
float speed = Mathf.Max(minScrollSpeed, Mathf.Abs(smoothVelocity.y));
float delta = cornerDist.y - targetCornerDistance;
float step = Mathf.Abs(speed) * deltaTime * Mathf.Sign(delta);
if ((delta < 0 && step < delta) || (delta > 0 && step > delta))
{
step = delta;
}
SetLayoutAnchoredPosition(layoutRectTransform.anchoredPosition + new Vector2(0, step));
}
}
private void UpdatePagesVisibilities()
{
// 视口宽度
float viewportWidth = viewport.rect.width;
// 视口左边缘相对 Layout 左上角的 x 坐标（通常正值）
float layoutViewLeft = UILayoutUtility.GetLayoutLT2ViewportLT(rectTransform, viewport).x;
// 视口左侧最近的不可见 page
// pageWidth + (pageWidth + pageSpace) * minIndex <= layoutViewLeft;
// 0.0001f 的作用：
// - 消除浮点误差的影响，如 2.0f 的实际结果可能是 2.0000001f
// - 解决 CeilToInt(2.0) == 2.0 的问题，保证 2.0 不被显示
// 视口内最左列
int minShownIndex = Mathf.CeilToInt((layoutViewLeft - pageSize.x) / (pageSize.x + pageSpace) + 0.0001f);
minShownIndex = Mathf.Max(minShownIndex, 0);
// 视口右侧最近的不可见 page
// (pageWidth + pageSpace) * minIndex => layoutViewLeft + viewportWidth;
// 视口内最右列
int maxShownIndex = Mathf.FloorToInt((layoutViewLeft + viewportWidth) / (pageSize.x + pageSpace) - 0.0001f);
maxShownIndex = Mathf.Min(maxShownIndex, pages.Count - 1);
if (currentMinShownIndex == -1)
{
for (int i = minShownIndex; i <= maxShownIndex; i++)
{
pages[i].ShowItem();
}
}
else if (currentMinShownIndex < minShownIndex || currentMaxShownIndex < maxShownIndex)
{
for (int i = currentMinShownIndex; i <= Mathf.Min(minShownIndex - 1, currentMaxShownIndex); i++)
{
pages[i].HideItem();
}
for (int i = Mathf.Max(minShownIndex, currentMaxShownIndex + 1); i <= maxShownIndex; i++)
{
pages[i].ShowItem();
}
}
else if (currentMinShownIndex > minShownIndex || currentMaxShownIndex > maxShownIndex)
{
for (int i = Mathf.Max(currentMinShownIndex, maxShownIndex + 1); i <= currentMaxShownIndex; i++)
{
pages[i].HideItem();
}
for (int i = minShownIndex; i <= Mathf.Min(maxShownIndex, currentMinShownIndex - 1); i++)
{
pages[i].ShowItem();
}
}
currentMinShownIndex = minShownIndex;
currentMaxShownIndex = maxShownIndex;
}
/// <summary>
/// 更新所有 row 的可见性，显示可见 rows 的元素，隐藏（回收）不可见 row 的元素。
/// </summary>
private void UpdateRowsVisibilities()
{
// 视口上边缘相对 Layout 左上角的 y 坐标（通常负值）
float layoutViewTop = UILayoutUtility.GetLayoutLT2ViewportLT(rectTransform, viewport).y;
float layoutViewBottom = layoutViewTop - viewport.rect.height;
// 视口上部最近的不可见 row
// -topPadding - rowSize.y - (rowSpace + rowSize.y) * minIndex < layoutViewTop;
// 视口内最上排
int minShownIndex = Mathf.CeilToInt(-(layoutViewTop + topPadding + rowSize.y) / (rowSpace + rowSize.y));
minShownIndex = Mathf.Max(minShownIndex, 0);
// 视口下部最近的不可见 row
// -topPadding - (rowSpace + rowSize.y) * maxIndex > layoutViewBottom;
// 视口内最下排
int maxShownIndex = Mathf.FloorToInt(-(layoutViewBottom + topPadding) / (rowSpace + rowSize.y));
maxShownIndex = Mathf.Min(maxShownIndex, rows.Count - 1);
if (lastMinShownIndex == -1)
{
for (int i = minShownIndex; i <= maxShownIndex; i++)
{
rows[i].ShowItems();
}
}
else if (lastMinShownIndex < minShownIndex || lastMaxShownIndex < maxShownIndex)
{
for (int i = lastMinShownIndex; i <= Mathf.Min(minShownIndex - 1, lastMaxShownIndex); i++)
{
rows[i].HideItems();
}
for (int i = Mathf.Max(minShownIndex, lastMaxShownIndex + 1); i <= maxShownIndex; i++)
{
rows[i].ShowItems();
}
}
else if (lastMinShownIndex > minShownIndex || lastMaxShownIndex > maxShownIndex)
{
for (int i = Mathf.Max(lastMinShownIndex, maxShownIndex + 1); i <= lastMaxShownIndex; i++)
{
rows[i].HideItems();
}
for (int i = minShownIndex; i <= Mathf.Min(maxShownIndex, lastMinShownIndex - 1); i++)
{
rows[i].ShowItems();
}
}
lastMinShownIndex = minShownIndex;
lastMaxShownIndex = maxShownIndex;
}
/// <summary>
/// 计算如果 layout 被移动到指定 anchoredPosition 时超出 viewport 的向量。
/// 用于约束 layout 在限定的范围内（不要跟随手指超出 viewport 的约束范围）。
/// </summary>
/// <param name="anchoredPosition">指定的 layout 锚定位置。</param>
/// <returns>偏移量。如果未超出则返回零值。</returns>
private Vector2 GetOutOffset(Vector2 anchoredPosition)
{
// 计入 viewport 和 page 尺寸差异
Vector2 deltaSize = (viewport.rect.size - scrolltoableLayout.GetItemSize(0)) * 0.5f;
// 目标位置时 viewport 和 layout 左上角之间的距离
Vector2 layoutLT2ViewLT = UILayoutUtility.GetLayoutLT2ViewportLT(layoutRectTransform, viewport);
layoutLT2ViewLT += layoutRectTransform.anchoredPosition - anchoredPosition;
if (direction == Direction.Horizontal)
{
// 左端超出（右滑）
if (layoutLT2ViewLT.x + deltaSize.x < 0)
{
return(new Vector2(layoutLT2ViewLT.x + deltaSize.x, 0));
}
// 右端超出（左滑）
else if (layoutLT2ViewLT.x + viewport.rect.width - deltaSize.x > layoutRectTransform.rect.width)
{
return(new Vector2(
layoutLT2ViewLT.x + viewport.rect.width - layoutRectTransform.rect.width - deltaSize.x, 0));
}
}
else
{
// 上端超出（下滑）
if (layoutLT2ViewLT.y - deltaSize.y > 0)
{
return(new Vector2(0, layoutLT2ViewLT.y - deltaSize.y));
}
// 下端超出（上滑）
else if (layoutLT2ViewLT.y - viewport.rect.height + deltaSize.y < -layoutRectTransform.rect.height)
{
return(new Vector2(
0,
layoutLT2ViewLT.y - viewport.rect.height + layoutRectTransform.rect.height + deltaSize.y));
}
}
return(Vector2.zero);
}