public ERect GetItemBound(int index)
{
int rowIndex = index / Span;
int columnIndex = index % Span;
var columnSize = ColumnSize;
int rowStartPoint = 0;
int columnStartPoint = 0;
int itemSize = 0;
if (!_hasUnevenRows)
{
itemSize = BaseItemSize;
rowStartPoint = ItemStartPoint + rowIndex * (BaseItemSize + ItemSpacing);
columnStartPoint = columnIndex * (columnSize + ColumnSpacing);
}
else if (_cached[index])
{
var updatedMaxItemSize = GetMaxItemSize(index);
itemSize = _itemSizes[index];
rowStartPoint = _accumulatedItemSizes[rowIndex] - updatedMaxItemSize + (updatedMaxItemSize - itemSize) / 2;
columnStartPoint = columnIndex * (columnSize + ColumnSpacing);
}
else
{
var oldMaxItemSize = GetMaxItemSize(index);
var measured = CollectionView.GetItemSize(index, ItemWidthConstraint, ItemHeightConstraint);
itemSize = IsHorizontal ? measured.Width : measured.Height;
if (itemSize != _itemSizes[index])
{
_itemSizes[index] = itemSize;
}
var updatedMaxItemSize = GetMaxItemSize(index);
if (oldMaxItemSize != updatedMaxItemSize)
{
UpdateAccumulatedItemSize(rowIndex, updatedMaxItemSize - oldMaxItemSize);
int columnStart = (index / Span) * Span;
for (int toUpdate = columnStart; toUpdate < index; toUpdate++)
{
if (_realizedItem.ContainsKey(toUpdate))
{
var updated = _realizedItem[toUpdate].View.Geometry;
if (IsHorizontal)
{
updated.X += (updatedMaxItemSize - oldMaxItemSize) / 2;
}
else
{
updated.Y += (updatedMaxItemSize - oldMaxItemSize) / 2;
}
_realizedItem[toUpdate].View.Geometry = updated;
}
}
CollectionView.ContentSizeUpdated();
}
rowStartPoint = _accumulatedItemSizes[rowIndex] - updatedMaxItemSize + (updatedMaxItemSize - itemSize) / 2;
columnStartPoint = columnIndex * (columnSize + ColumnSpacing);
_cached[index] = true;
}
return(IsHorizontal ?
new ERect(rowStartPoint, columnStartPoint, itemSize, columnSize) :
new ERect(columnStartPoint, rowStartPoint, columnSize, itemSize));
}
public void UpdateSpan(int span)
{
Span = span;
InitializeMeasureCache();
CollectionView.RequestLayoutItems();
}
