void InitializeMeasureCache()
{
_baseItemSize = 0;
_scrollCanvasSize = new Size(0, 0);
_lastLayoutedBound = new Rect(0, 0, 0, 0);
if (_allocatedSize.Width <= 0 || _allocatedSize.Height <= 0)
{
return;
}
if (!_hasUnevenRows)
{
CollectionView !.ContentSizeUpdated();
return;
}
int n = CollectionView !.Count;
_itemSizes = new List <double>();
_cached = new List <bool>();
_accumulatedItemSizes = new List <double>();
for (int i = 0; i < n; i++)
{
_cached.Add(false);
_itemSizes.Add(BaseItemSize);
if (i % Span == 0)
{
int accIndex = i / Span;
_accumulatedItemSizes.Add((accIndex > 0 ? (_accumulatedItemSizes[accIndex - 1] + ItemSpacing) : ItemStartPoint) + _itemSizes[i]);
}
}
CollectionView !.ContentSizeUpdated();
}
void UpdateFooterPosition()
{
if (_footer == null)
{
return;
}
var point = new Point();
if (IsHorizontal)
{
point.X += (GetScrollCanvasSize().Width - _footerSize.Width);
}
else
{
point.Y += (GetScrollCanvasSize().Height - _footerSize.Height);
}
var bound = new Rect(point, _footerSize);
if (IsHorizontal)
{
bound.Height = _allocatedSize.Height;
}
else
{
bound.Width = _allocatedSize.Width;
}
_footer.UpdateBounds(bound);
}
int GetEndIndex(Rect bound)
{
if (!_hasUnevenRows)
{
return(GetEndIndex(bound, BaseItemSize + ItemSpacing));
}
return((FindFirstGreaterOrEqualTo(_accumulatedItemSizes, ViewPortEndPoint(bound)) + 1) * Span - 1);
}
int GetStartIndex(Rect bound)
{
if (!_hasUnevenRows)
{
return(GetStartIndex(bound, BaseItemSize + ItemSpacing));
}
return(FindFirstGreaterOrEqualTo(_accumulatedItemSizes, ViewPortStartPoint(bound)));
}
public static void UpdateBounds(this View view, Rect bounds)
{
if (view.Size.Width != bounds.Width || view.Size.Height != bounds.Height)
{
view.Size = bounds.Size.ToNative();
}
if (view.Position.X != bounds.X || view.Position.Y != bounds.Y)
{
view.Position = bounds.Location.ToNative();
}
}
public void LayoutItems(Rect bound, bool force)
{
if (_allocatedSize.Width <= 0 || _allocatedSize.Height <= 0)
{
return;
}
// TODO : need to optimization. it was frequently called with similar bound value.
if (!ShouldRearrange(bound) && !force)
{
return;
}
_isLayouting = true;
_lastLayoutedBound = bound;
int padding = Span;
int startIndex = Math.Max(GetStartIndex(bound) - padding * 2, 0);
int endIndex = Math.Min(GetEndIndex(bound) + padding * 2, CollectionView !.Count - 1);
foreach (var index in _realizedItem.Keys.ToList())
{
if (index < startIndex || index > endIndex)
{
CollectionView !.UnrealizeView(_realizedItem[index].View);
_realizedItem.Remove(index);
}
}
for (int i = startIndex; i <= endIndex; i++)
{
View?itemView = null;
if (!_realizedItem.ContainsKey(i))
{
var view = CollectionView !.RealizeView(i);
_realizedItem[i] = new RealizedItem(view, i);
itemView = view;
}
else
{
itemView = _realizedItem[i].View;
}
var itemBound = GetItemBound(i);
itemView.UpdateBounds(itemBound);
}
_isLayouting = false;
}
public void SetHeader(View?header, Size size)
{
bool contentSizeChanged = false;
if (IsHorizontal)
{
if (_headerSize.Width != size.Width)
{
contentSizeChanged = true;
}
}
else
{
if (_headerSize.Height != size.Height)
{
contentSizeChanged = true;
}
}
_header = header;
_headerSize = size;
if (contentSizeChanged)
{
InitializeMeasureCache();
CollectionView !.ContentSizeUpdated();
}
if (_header != null)
{
var bound = new Rect(0, 0, _headerSize.Width, _headerSize.Height);
if (IsHorizontal)
{
bound.Height = _allocatedSize.Height;
}
else
{
bound.Width = _allocatedSize.Width;
}
_header.UpdateBounds(bound);
}
}
bool ShouldRearrange(Rect viewport)
{
if (_isLayouting)
{
return(false);
}
if (_lastLayoutedBound.Size != viewport.Size)
{
return(true);
}
var diff = IsHorizontal ? Math.Abs(_lastLayoutedBound.X - viewport.X) : Math.Abs(_lastLayoutedBound.Y - viewport.Y);
if (diff > BaseItemSize)
{
return(true);
}
return(false);
}
public static void UpdateBounds(this View view, Rect bounds)
{
view.Size = bounds.Size.ToNative();
view.Position = bounds.Location.ToNative();
}
double ViewPortSize(Rect viewPort)
{
return(IsHorizontal ? viewPort.Width : viewPort.Height);
}
double ViewPortEndPoint(Rect viewPort)
{
return(ViewPortStartPoint(viewPort) + ViewPortSize(viewPort));
}
double ViewPortStartPoint(Rect viewPort)
{
return(IsHorizontal ? viewPort.X : viewPort.Y);
}
int GetEndIndex(Rect bound, double itemSize)
{
return((int)Math.Ceiling(ViewPortEndPoint(bound) / (double)itemSize) - 1);
}
int GetStartIndex(Rect bound, double itemSize)
{
return((int)((ViewPortStartPoint(bound) - ItemStartPoint) / itemSize));
}
public static void UpdateBounds(this EvasObject view, Rect bounds)
{
view.Geometry = new ERect((int)bounds.X, (int)bounds.Y, (int)bounds.Width, (int)bounds.Height);
}
public static Rect ToDP(this TRect rect)
{
return(new Rect(ConvertToScaledDP(rect.X), ConvertToScaledDP(rect.Y), ConvertToScaledDP(rect.Width), ConvertToScaledDP(rect.Height)));
}
